поменяла класс реализацию для специализации на использование параметров в запросах. и формы для специализации донастроила вроде... только айдишники не перезаписываются (удалила 4 айдишник - следующим добавилась специализация с айдишником 5)

BeautySalon/BeautySalon/FormSpecialisation.Designer.cs

@@ -28,12 +28,57 @@
         /// </summary>
         private void InitializeComponent()
         {
-            this.components = new System.ComponentModel.Container();
+            buttonSave = new Button();
-            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
+            textBoxNameSpecialisation = new TextBox();
-            this.ClientSize = new System.Drawing.Size(800, 450);
+            buttonCancel = new Button();
-            this.Text = "FormSpecialisation";
+            SuspendLayout();
+            // 
+            // buttonSave
+            // 
+            buttonSave.Location = new Point(37, 86);
+            buttonSave.Name = "buttonSave";
+            buttonSave.Size = new Size(133, 44);
+            buttonSave.TabIndex = 0;
+            buttonSave.Text = "Сохранить";
+            buttonSave.UseVisualStyleBackColor = true;
+            buttonSave.Click += buttonSave_Click;
+            // 
+            // textBoxNameSpecialisation
+            // 
+            textBoxNameSpecialisation.Location = new Point(37, 33);
+            textBoxNameSpecialisation.Name = "textBoxNameSpecialisation";
+            textBoxNameSpecialisation.Size = new Size(274, 27);
+            textBoxNameSpecialisation.TabIndex = 1;
+            // 
+            // buttonCancel
+            // 
+            buttonCancel.Location = new Point(178, 86);
+            buttonCancel.Name = "buttonCancel";
+            buttonCancel.Size = new Size(133, 44);
+            buttonCancel.TabIndex = 2;
+            buttonCancel.Text = "Отмена";
+            buttonCancel.UseVisualStyleBackColor = true;
+            buttonCancel.Click += buttonCancel_Click;
+            // 
+            // FormSpecialisation
+            // 
+            AutoScaleDimensions = new SizeF(8F, 20F);
+            AutoScaleMode = AutoScaleMode.Font;
+            ClientSize = new Size(345, 170);
+            Controls.Add(buttonCancel);
+            Controls.Add(textBoxNameSpecialisation);
+            Controls.Add(buttonSave);
+            Name = "FormSpecialisation";
+            Text = "Специализация";
+            Load += FormSpecialisation_Load;
+            ResumeLayout(false);
+            PerformLayout();
         }
 
         #endregion
+
+        private Button buttonSave;
+        private TextBox textBoxNameSpecialisation;
+        private Button buttonCancel;
     }
 }

BeautySalon/BeautySalon/FormSpecialisation.cs

@@ -1,4 +1,6 @@
-using System;
+using BeautySalonDBModels;
+using BeautySalonDBModels.Models;
+using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Data;
@@ -12,9 +14,77 @@ namespace BeautySalon
 {
     public partial class FormSpecialisation : Form
     {
-        public FormSpecialisation()
+
+        private readonly AbstractWorkWithStorage<Specialisation> storage;
+
+        private int? _id;
+        public int Id
         {
+            set { _id = value; }
+        }
+
+        public FormSpecialisation(AbstractWorkWithStorage<Specialisation> storage)
+        {
+            this.storage = storage;
             InitializeComponent();
         }
+
+        private void buttonSave_Click(object sender, EventArgs e)
+        {
+            try
+            {
+                if (_id != null)
+                {
+                    var newSpecialisation = new Specialisation
+                    {
+                        SpecialisationId = _id ?? 0,
+                        Name = textBoxNameSpecialisation.Text,
+                    };
+
+                    storage.Update(newSpecialisation);
+                }
+                else
+                {
+                    var specialisation = new Specialisation
+                    {
+                        Name = textBoxNameSpecialisation.Text,
+                    };
+                    storage.Add(specialisation);
+                }
+                DialogResult = DialogResult.OK;
+                Close();
+            }
+            catch (Exception ex)
+            {
+                MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
+            }
+
+        }
+
+        private void buttonCancel_Click(object sender, EventArgs e)
+        {
+            DialogResult = DialogResult.Cancel; Close();    
+        }
+
+        private void FormSpecialisation_Load(object sender, EventArgs e)
+        {
+            if (_id.HasValue)
+            {
+                try
+                {
+                    var specialisationObject = storage.GetObject(_id.Value);
+
+                    if (specialisationObject != null)
+                    {
+                        textBoxNameSpecialisation.Text = specialisationObject.Name;
+                    }
+                }
+                catch (Exception ex)
+                {
+                    MessageBox.Show(ex.Message, "Ошибка", MessageBoxButtons.OK,
+                    MessageBoxIcon.Error);
+                }
+            }
+        }
     }
 }

BeautySalon/BeautySalonDBModels/Implements/SpecialisationDB.cs

@@ -14,18 +14,20 @@ namespace BeautySalonDBModels.Implements
         {
             using var conn = GetConnection();
             conn.Open();
-            using var cmd = new NpgsqlCommand("INSERT INTO specialisations (specialisation_name) " +
+            using var cmd = new NpgsqlCommand("INSERT INTO specialisations (specialisation_id, specialisation_name) VALUES (nextval('seq_specialisation'), @Name)", conn);
-                "VALUES (@Name)", conn);
             cmd.Parameters.AddWithValue("@Name", specialisation.Name);
             cmd.ExecuteNonQuery();
         }
 
+
         public override Specialisation? GetObject(int id)
         {
             using var conn = GetConnection();
             conn.Open();
-            using var cmd = new NpgsqlCommand("SELECT * FROM specialisations WHERE specialisation_id = {id}", conn);
+            using var cmd = new NpgsqlCommand("SELECT * FROM specialisations WHERE specialisation_id = @id", conn);
+            cmd.Parameters.AddWithValue("@id", id);
             using var reader = cmd.ExecuteReader();
+
             if (reader.Read())
             {
                 return new Specialisation
@@ -58,10 +60,14 @@ namespace BeautySalonDBModels.Implements
         public override Specialisation? Remove(int id)
         {
             var specialisation = GetObject(id);
-            using var conn = GetConnection();
+            if (specialisation != null)
-            conn.Open();
+            {
-            using var cmd = new NpgsqlCommand("delete from specialisations where specialisation_id = {id}", conn);
+                using var conn = GetConnection();
-            cmd.ExecuteNonQuery();
+                conn.Open();
+                using var cmd = new NpgsqlCommand("delete from specialisations where specialisation_id = @SpecialisationId", conn);
+                cmd.Parameters.AddWithValue("@SpecialisationId", id);
+                cmd.ExecuteNonQuery();
+            }
             return specialisation;
         }
 
@@ -69,9 +75,11 @@ namespace BeautySalonDBModels.Implements
         {
             using var conn = GetConnection();
             conn.Open();
-            using var cmd = new NpgsqlCommand("update specialisation set specialisation_name = {specialisation.Name}, " +
+            using var cmd = new NpgsqlCommand("UPDATE specialisations SET specialisation_name = @Name WHERE specialisation_id = @SpecialisationId", conn);
-                "where specialisation_id = {specialisation.SpecialisationId}", conn);
+            cmd.Parameters.AddWithValue("@Name", specialisation.Name);
+            cmd.Parameters.AddWithValue("@SpecialisationId", specialisation.SpecialisationId);
             cmd.ExecuteNonQuery();
         }
+
     }
 }