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SUBD_Car_rent/Forms/FormMain.Designer.cs

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+namespace Forms
+{
+    partial class FormMain
+    {
+        /// <summary>
+        /// Required designer variable.
+        /// </summary>
+        private System.ComponentModel.IContainer components = null;
+
+        /// <summary>
+        /// Clean up any resources being used.
+        /// </summary>
+        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing && (components != null))
+            {
+                components.Dispose();
+            }
+            base.Dispose(disposing);
+        }
+
+        #region Windows Form Designer generated code
+
+        /// <summary>
+        /// Required method for Designer support - do not modify
+        /// the contents of this method with the code editor.
+        /// </summary>
+        private void InitializeComponent()
+        {
+            button1 = new Button();
+            dataGridView1 = new DataGridView();
+            ((System.ComponentModel.ISupportInitialize)dataGridView1).BeginInit();
+            SuspendLayout();
+            // 
+            // button1
+            // 
+            button1.Location = new Point(12, 12);
+            button1.Name = "button1";
+            button1.Size = new Size(75, 23);
+            button1.TabIndex = 0;
+            button1.Text = "button1";
+            button1.UseVisualStyleBackColor = true;
+            button1.Click += button1_Click;
+            // 
+            // dataGridView1
+            // 
+            dataGridView1.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.AutoSize;
+            dataGridView1.Location = new Point(12, 41);
+            dataGridView1.Name = "dataGridView1";
+            dataGridView1.RowTemplate.Height = 25;
+            dataGridView1.Size = new Size(776, 397);
+            dataGridView1.TabIndex = 1;
+            // 
+            // FormMain
+            // 
+            AutoScaleDimensions = new SizeF(7F, 15F);
+            AutoScaleMode = AutoScaleMode.Font;
+            ClientSize = new Size(800, 450);
+            Controls.Add(dataGridView1);
+            Controls.Add(button1);
+            Name = "FormMain";
+            Text = "FormMain";
+            ((System.ComponentModel.ISupportInitialize)dataGridView1).EndInit();
+            ResumeLayout(false);
+        }
+
+        #endregion
+
+        private Button button1;
+        private DataGridView dataGridView1;
+    }
+}

SUBD_Car_rent/Forms/FormMain.cs

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+using database;
+
+namespace Forms
+{
+    public partial class FormMain : Form
+    {
+        
+        public FormMain()
+        {
+            InitializeComponent();
+        }
+
+        /*
+        private Abstractions bd = new Implementation();
+        private void button1_Click(object sender, EventArgs e)
+        {
+            List<Branch> branches = bd.GetBranches();
+
+            // Очищаем dataGridView1 перед заполнением новыми данными
+            dataGridView1.Rows.Clear();
+
+            // Предварительно определяем столбцы, если это не было сделано ранее
+            if (dataGridView1.ColumnCount == 0)
+            {
+                dataGridView1.Columns.Add("Id", "ID");
+                dataGridView1.Columns.Add("Name", "Name");
+                dataGridView1.Columns.Add("Address", "Address");
+                dataGridView1.Columns.Add("Phone", "Phone");
+                dataGridView1.Columns.Add("WorkingHours", "Working Hours");
+            }
+
+            // Заполняем dataGridView1 данными из списка branches
+            foreach (Branch branch in branches)
+            {
+                dataGridView1.Rows.Add(branch.Id, branch.Name, branch.Address, branch.Phone, branch.WorkingHours);
+            }
+        }
+        */
+    }
+}

SUBD_Car_rent/Forms/FormMain.resx

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+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <!--
+    Microsoft ResX Schema 
+
+    Version 2.0
+
+    The primary goals of this format is to allow a simple XML format
+    that is mostly human readable. The generation and parsing of the
+    various data types are done through the TypeConverter classes
+    associated with the data types.
+
+    Example:
+
+    ... ado.net/XML headers & schema ...
+    <resheader name="resmimetype">text/microsoft-resx</resheader>
+    <resheader name="version">2.0</resheader>
+    <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
+    <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
+    <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
+        <value>[base64 mime encoded serialized .NET Framework object]</value>
+    </data>
+    <data name="Icon1" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
+        <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
+        <comment>This is a comment</comment>
+    </data>
+
+    There are any number of "resheader" rows that contain simple
+    name/value pairs.
+
+    Each data row contains a name, and value. The row also contains a
+    type or mimetype. Type corresponds to a .NET class that support
+    text/value conversion through the TypeConverter architecture.
+    Classes that don't support this are serialized and stored with the
+    mimetype set.
+
+    The mimetype is used for serialized objects, and tells the
+    ResXResourceReader how to depersist the object. This is currently not
+    extensible. For a given mimetype the value must be set accordingly:
+
+    Note - application/x-microsoft.net.object.binary.base64 is the format
+    that the ResXResourceWriter will generate, however the reader can
+    read any of the formats listed below.
+
+    mimetype: application/x-microsoft.net.object.binary.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
+            : and then encoded with base64 encoding.
+    
+    mimetype: application/x-microsoft.net.object.soap.base64
+    value   : The object must be serialized with
+            : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
+            : and then encoded with base64 encoding.
+
+    mimetype: application/x-microsoft.net.object.bytearray.base64
+    value   : The object must be serialized into a byte array
+            : using a System.ComponentModel.TypeConverter
+            : and then encoded with base64 encoding.
+    -->
+  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
+    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
+    <xsd:element name="root" msdata:IsDataSet="true">
+      <xsd:complexType>
+        <xsd:choice maxOccurs="unbounded">
+          <xsd:element name="metadata">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" />
+              </xsd:sequence>
+              <xsd:attribute name="name" use="required" type="xsd:string" />
+              <xsd:attribute name="type" type="xsd:string" />
+              <xsd:attribute name="mimetype" type="xsd:string" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="assembly">
+            <xsd:complexType>
+              <xsd:attribute name="alias" type="xsd:string" />
+              <xsd:attribute name="name" type="xsd:string" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="data">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
+              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
+              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
+              <xsd:attribute ref="xml:space" />
+            </xsd:complexType>
+          </xsd:element>
+          <xsd:element name="resheader">
+            <xsd:complexType>
+              <xsd:sequence>
+                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
+              </xsd:sequence>
+              <xsd:attribute name="name" type="xsd:string" use="required" />
+            </xsd:complexType>
+          </xsd:element>
+        </xsd:choice>
+      </xsd:complexType>
+    </xsd:element>
+  </xsd:schema>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+</root>

SUBD_Car_rent/Forms/Forms.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>WinExe</OutputType>
+    <TargetFramework>net6.0-windows</TargetFramework>
+    <Nullable>enable</Nullable>
+    <UseWindowsForms>true</UseWindowsForms>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\databaseAbstractions\database.csproj" />
+  </ItemGroup>
+
+</Project>

SUBD_Car_rent/Forms/Program.cs

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+namespace Forms
+{
+    internal static class Program
+    {
+        /// <summary>
+        ///  The main entry point for the application.
+        /// </summary>
+        [STAThread]
+        static void Main()
+        {
+            // To customize application configuration such as set high DPI settings or default font,
+            // see https://aka.ms/applicationconfiguration.
+            ApplicationConfiguration.Initialize();
+            Application.Run(new FormMain());
+        }
+    }
+}

SUBD_Car_rent/SUBD_Car_rent.sln

@@ -0,0 +1,31 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.8.34309.116
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "database", "databaseAbstractions\database.csproj", "{874A3D9B-6051-4823-9A3B-725C71FDC245}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Forms", "Forms\Forms.csproj", "{318E26AF-A4DC-4863-B829-DBD4B63DC0D7}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{874A3D9B-6051-4823-9A3B-725C71FDC245}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{874A3D9B-6051-4823-9A3B-725C71FDC245}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{874A3D9B-6051-4823-9A3B-725C71FDC245}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{874A3D9B-6051-4823-9A3B-725C71FDC245}.Release|Any CPU.Build.0 = Release|Any CPU
+		{318E26AF-A4DC-4863-B829-DBD4B63DC0D7}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{318E26AF-A4DC-4863-B829-DBD4B63DC0D7}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{318E26AF-A4DC-4863-B829-DBD4B63DC0D7}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{318E26AF-A4DC-4863-B829-DBD4B63DC0D7}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {C9647B13-C74A-4FAE-A110-8C99AF4E3DEC}
+	EndGlobalSection
+EndGlobal

SUBD_Car_rent/databaseAbstractions/Abstractions.cs

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+namespace database
+{
+    public abstract class Abstractions
+    {
+
+        // CDUD операции для каждой сущности
+
+        // Car
+        public abstract void AddCar(Car car);
+        public abstract List<Car> GetCars();
+        public abstract Car GetCarById(int id);
+        public abstract void UpdateCar(Car car);
+        public abstract void DeleteCar(int id);
+
+        // Client
+        public abstract void AddClient(Client client);
+        public abstract Client GetClientById(int id);
+        public abstract List<Client> GetClients();
+        public abstract void UpdateClient(Client client);
+        public abstract void DeleteClient(int id);
+
+        // Rental
+        public abstract void AddRental(Rental rental);
+        public abstract Rental GetRentalById(int id);
+        public abstract List<Rental> GetRentals();
+        public abstract void UpdateRental(Rental rental);
+        public abstract void DeleteRental(int id);
+
+        // CarModel
+        public abstract void AddCarModel(CarModel carModel);
+        public abstract CarModel GetCarModelById(int id);
+        public abstract List<CarModel> GetCarModels();
+        public abstract void UpdateCarModel(CarModel carModel);
+        public abstract void DeleteCarModel(int id);
+
+        // Branch
+        public abstract void AddBranch(Branch branch);
+        public abstract Branch GetBranchById(int id);
+        public abstract List<Branch> GetBranches();
+        public abstract void UpdateBranch(Branch branch);
+        public abstract void DeleteBranch(int id);
+    }
+}

SUBD_Car_rent/databaseAbstractions/Implementation.cs

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+using Npgsql;
+
+namespace database
+{
+    public class Implementation : Abstractions
+    {
+        private NpgsqlConnection GetConnection()
+        {
+            return new NpgsqlConnection("Host=172.18.241.131;Username=tim;Database=carrent;");
+        }
+
+        // CDUD операции для каждой сущности
+
+        // Car
+        public override void AddCar(Car car)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"INSERT INTO car (id, model_id, branch_id, year, mileage, status_id) VALUES ({car.Id}, {car.ModelId}, {car.BranchId}, {car.Year}, {car.Mileage}, {car.StatusId})", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override List<Car> GetCars()
+        {
+            var cars = new List<Car>();
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand("SELECT * FROM car", conn);
+            using var reader = cmd.ExecuteReader();
+            while (reader.Read())
+            {
+                cars.Add(new Car
+                {
+                    Id = reader.GetInt32(0),
+                    ModelId = reader.GetInt32(1),
+                    BranchId = reader.GetInt32(2),
+                    Year = reader.GetInt32(3),
+                    Mileage = reader.GetInt32(4),
+                    StatusId = reader.GetInt32(5)
+                });
+            }
+            return cars;
+        }
+
+        public override Car GetCarById(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"SELECT * FROM car WHERE id = {id}", conn);
+            using var reader = cmd.ExecuteReader();
+            if (reader.Read())
+            {
+                return new Car
+                {
+                    Id = reader.GetInt32(0),
+                    ModelId = reader.GetInt32(1),
+                    BranchId = reader.GetInt32(2),
+                    Year = reader.GetInt32(3),
+                    Mileage = reader.GetInt32(4),
+                    StatusId = reader.GetInt32(5)
+                };
+            }
+            return null;
+        }
+
+        public override void UpdateCar(Car car)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"UPDATE car SET model_id = {car.ModelId}, branch_id = {car.BranchId}, year = {car.Year}, mileage = {car.Mileage}, status_id = {car.StatusId} WHERE id = {car.Id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override void DeleteCar(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"DELETE FROM car WHERE id = {id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        // Client
+        public override void AddClient(Client client)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"INSERT INTO client (id, name, surname, address, phone, email) VALUES ({client.Id}, '{client.Name}', '{client.Surname}', '{client.Address}', '{client.Phone}', '{client.Email}')", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override List<Client> GetClients()
+        {
+            var clients = new List<Client>();
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand("SELECT * FROM client", conn);
+            using var reader = cmd.ExecuteReader();
+            while (reader.Read())
+            {
+                clients.Add(new Client
+                {
+                    Id = reader.GetInt32(0),
+                    Name = reader.GetString(1),
+                    Surname = reader.GetString(2),
+                    Address = reader.GetString(3),
+                    Phone = reader.GetString(4),
+                    Email = reader.GetString(5)
+                });
+            }
+            return clients;
+        }
+
+        public override Client GetClientById(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"SELECT * FROM client WHERE id = {id}", conn);
+            using var reader = cmd.ExecuteReader();
+            if (reader.Read())
+            {
+                return new Client
+                {
+                    Id = reader.GetInt32(0),
+                    Name = reader.GetString(1),
+                    Surname = reader.GetString(2),
+                    Address = reader.GetString(3),
+                    Phone = reader.GetString(4),
+                    Email = reader.GetString(5)
+                };
+            }
+            return null;
+        }
+
+        public override void UpdateClient(Client client)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"UPDATE client SET name = '{client.Name}', surname = '{client.Surname}', address = '{client.Address}', phone = '{client.Phone}', email = '{client.Email}' WHERE id = {client.Id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override void DeleteClient(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"DELETE FROM client WHERE id = {id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        // Rental
+        public override void AddRental(Rental rental)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"INSERT INTO rental (id, car_id, client_id, start_date, end_date, cost) VALUES ({rental.Id}, {rental.CarId}, {rental.ClientId}, '{rental.StartDate}', '{rental.EndDate}', {rental.Cost})", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override List<Rental> GetRentals()
+        {
+            var rentals = new List<Rental>();
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand("SELECT * FROM rental", conn);
+            using var reader = cmd.ExecuteReader();
+            while (reader.Read())
+            {
+                rentals.Add(new Rental
+                {
+                    Id = reader.GetInt32(0),
+                    CarId = reader.GetInt32(1),
+                    ClientId = reader.GetInt32(2),
+                    StartDate = reader.GetDateTime(3),
+                    EndDate = reader.GetDateTime(4),
+                    Cost = reader.GetDecimal(5)
+                });
+            }
+            return rentals;
+        }
+
+        public override Rental GetRentalById(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"SELECT * FROM rental WHERE id = {id}", conn);
+            using var reader = cmd.ExecuteReader();
+            if (reader.Read())
+            {
+                return new Rental
+                {
+                    Id = reader.GetInt32(0),
+                    CarId = reader.GetInt32(1),
+                    ClientId = reader.GetInt32(2),
+                    StartDate = reader.GetDateTime(3),
+                    EndDate = reader.GetDateTime(4),
+                    Cost = reader.GetDecimal(5)
+                };
+            }
+            return null;
+        }
+
+        public override void UpdateRental(Rental rental)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"UPDATE rental SET car_id = {rental.CarId}, client_id = {rental.ClientId}, start_date = '{rental.StartDate}', end_date = '{rental.EndDate}', cost = {rental.Cost} WHERE id = {rental.Id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override void DeleteRental(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"DELETE FROM rental WHERE id = {id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        // CarModel
+        public override void AddCarModel(CarModel carModel)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"INSERT INTO car_model (id, brand, model, year, body_type_id, seats) VALUES ({carModel.Id}, '{carModel.Brand}', '{carModel.Model}', {carModel.Year}, {carModel.BodyTypeId}, {carModel.Seats})", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override List<CarModel> GetCarModels()
+        {
+            var carModels = new List<CarModel>();
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand("SELECT * FROM car_model", conn);
+            using var reader = cmd.ExecuteReader();
+            while (reader.Read())
+            {
+                carModels.Add(new CarModel
+                {
+                    Id = reader.GetInt32(0),
+                    Brand = reader.GetString(1),
+                    Model = reader.GetString(2),
+                    Year = reader.GetInt32(3),
+                    BodyTypeId = reader.GetInt32(4),
+                    Seats = reader.GetInt32(5)
+                });
+            }
+            return carModels;
+        }
+
+        public override CarModel GetCarModelById(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"SELECT * FROM car_model WHERE id = {id}", conn);
+            using var reader = cmd.ExecuteReader();
+            if (reader.Read())
+            {
+                return new CarModel
+                {
+                    Id = reader.GetInt32(0),
+                    Brand = reader.GetString(1),
+                    Model = reader.GetString(2),
+                    Year = reader.GetInt32(3),
+                    BodyTypeId = reader.GetInt32(4),
+                    Seats = reader.GetInt32(5)
+                };
+            }
+            return null;
+        }
+        public override void UpdateCarModel(CarModel carModel)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"UPDATE car_model SET brand = '{carModel.Brand}', model = '{carModel.Model}', year = {carModel.Year}, body_type_id = {carModel.BodyTypeId}, seats = {carModel.Seats} WHERE id = {carModel.Id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override void DeleteCarModel(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"DELETE FROM car_model WHERE id = {id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        // Branch
+        public override void AddBranch(Branch branch)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"INSERT INTO branch (id, name, address, phone, working_hours) VALUES ({branch.Id}, '{branch.Name}', '{branch.Address}', '{branch.Phone}', '{branch.WorkingHours}')", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override List<Branch> GetBranches()
+        {
+            var branches = new List<Branch>();
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand("SELECT * FROM branch", conn);
+            using var reader = cmd.ExecuteReader();
+            while (reader.Read())
+            {
+                branches.Add(new Branch
+                {
+                    Id = reader.GetInt32(0),
+                    Name = reader.GetString(1),
+                    Address = reader.GetString(2),
+                    Phone = reader.GetString(3),
+                    WorkingHours = reader.GetString(4)
+                });
+            }
+            return branches;
+        }
+
+        public override Branch GetBranchById(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"SELECT * FROM branch WHERE id = {id}", conn);
+            using var reader = cmd.ExecuteReader();
+            if (reader.Read())
+            {
+                return new Branch
+                {
+                    Id = reader.GetInt32(0),
+                    Name = reader.GetString(1),
+                    Address = reader.GetString(2),
+                    Phone = reader.GetString(3),
+                    WorkingHours = reader.GetString(4)
+                };
+            }
+            return null;
+        }
+
+        public override void UpdateBranch(Branch branch)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"UPDATE branch SET name = '{branch.Name}', address = '{branch.Address}', phone = '{branch.Phone}', working_hours = '{branch.WorkingHours}' WHERE id = {branch.Id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+
+        public override void DeleteBranch(int id)
+        {
+            using var conn = GetConnection();
+            conn.Open();
+            using var cmd = new NpgsqlCommand($"DELETE FROM branch WHERE id = {id}", conn);
+            cmd.ExecuteNonQuery();
+        }
+    }
+}

SUBD_Car_rent/databaseAbstractions/database.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Npgsql" Version="8.0.2" />
+  </ItemGroup>
+
+</Project>

SUBD_Car_rent/databaseAbstractions/models.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace database
+{
+    // Определение моделей данных
+
+    public class Car
+    {
+        public int Id { get; set; }
+        public int ModelId { get; set; }
+        public int BranchId { get; set; }
+        public int Year { get; set; }
+        public int Mileage { get; set; }
+        public int StatusId { get; set; }
+    }
+
+    public class Client
+    {
+        public int Id { get; set; }
+        public string Name { get; set; }
+        public string Surname { get; set; }
+        public string Address { get; set; }
+        public string Phone { get; set; }
+        public string Email { get; set; }
+    }
+
+    public class Rental
+    {
+        public int Id { get; set; }
+        public int CarId { get; set; }
+        public int ClientId { get; set; }
+        public DateTime StartDate { get; set; }
+        public DateTime EndDate { get; set; }
+        public decimal Cost { get; set; }
+    }
+
+    public class CarModel
+    {
+        public int Id { get; set; }
+        public string Brand { get; set; }
+        public string Model { get; set; }
+        public int Year { get; set; }
+        public int BodyTypeId { get; set; }
+        public int Seats { get; set; }
+    }
+
+    public class Branch
+    {
+        public int Id { get; set; }
+        public string Name { get; set; }
+        public string Address { get; set; }
+        public string Phone { get; set; }
+        public string WorkingHours { get; set; }
+    }
+}