Вроде всё готово и работает.

TransportCompany/TransportCompany/FormCheckTimeJoin.Designer.cs

@@ -0,0 +1,135 @@
+namespace TransportCompany
+{
+    partial class FormCheckTimeJoin
+    {
+        /// <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()
+        {
+            textBoxFirstCheck = new TextBox();
+            groupBoxFirst = new GroupBox();
+            buttonCheckFirstJoin = new Button();
+            groupBoxSecond = new GroupBox();
+            textBoxSecondCheck = new TextBox();
+            buttonCheckSecondJoin = new Button();
+            buttonCancel = new Button();
+            groupBoxFirst.SuspendLayout();
+            groupBoxSecond.SuspendLayout();
+            SuspendLayout();
+            // 
+            // textBoxFirstCheck
+            // 
+            textBoxFirstCheck.Location = new Point(312, 42);
+            textBoxFirstCheck.Name = "textBoxFirstCheck";
+            textBoxFirstCheck.Size = new Size(228, 27);
+            textBoxFirstCheck.TabIndex = 0;
+            // 
+            // groupBoxFirst
+            // 
+            groupBoxFirst.Controls.Add(buttonCheckFirstJoin);
+            groupBoxFirst.Controls.Add(textBoxFirstCheck);
+            groupBoxFirst.Location = new Point(12, 12);
+            groupBoxFirst.Name = "groupBoxFirst";
+            groupBoxFirst.Size = new Size(580, 91);
+            groupBoxFirst.TabIndex = 1;
+            groupBoxFirst.TabStop = false;
+            groupBoxFirst.Text = "Для первого запроса";
+            // 
+            // buttonCheckFirstJoin
+            // 
+            buttonCheckFirstJoin.Location = new Point(65, 42);
+            buttonCheckFirstJoin.Name = "buttonCheckFirstJoin";
+            buttonCheckFirstJoin.Size = new Size(195, 29);
+            buttonCheckFirstJoin.TabIndex = 1;
+            buttonCheckFirstJoin.Text = "Произвести замер";
+            buttonCheckFirstJoin.UseVisualStyleBackColor = true;
+            buttonCheckFirstJoin.Click += ButtonCheckFirstJoin_Click;
+            // 
+            // groupBoxSecond
+            // 
+            groupBoxSecond.Controls.Add(textBoxSecondCheck);
+            groupBoxSecond.Controls.Add(buttonCheckSecondJoin);
+            groupBoxSecond.Location = new Point(12, 109);
+            groupBoxSecond.Name = "groupBoxSecond";
+            groupBoxSecond.Size = new Size(580, 95);
+            groupBoxSecond.TabIndex = 2;
+            groupBoxSecond.TabStop = false;
+            groupBoxSecond.Text = "Для второго запроса";
+            // 
+            // textBoxSecondCheck
+            // 
+            textBoxSecondCheck.Location = new Point(312, 41);
+            textBoxSecondCheck.Name = "textBoxSecondCheck";
+            textBoxSecondCheck.Size = new Size(228, 27);
+            textBoxSecondCheck.TabIndex = 1;
+            // 
+            // buttonCheckSecondJoin
+            // 
+            buttonCheckSecondJoin.Location = new Point(65, 41);
+            buttonCheckSecondJoin.Name = "buttonCheckSecondJoin";
+            buttonCheckSecondJoin.Size = new Size(195, 29);
+            buttonCheckSecondJoin.TabIndex = 0;
+            buttonCheckSecondJoin.Text = "Произвести замер";
+            buttonCheckSecondJoin.UseVisualStyleBackColor = true;
+            buttonCheckSecondJoin.Click += ButtonCheckSecondJoin_Click;
+            // 
+            // buttonCancel
+            // 
+            buttonCancel.Location = new Point(452, 220);
+            buttonCancel.Name = "buttonCancel";
+            buttonCancel.Size = new Size(140, 29);
+            buttonCancel.TabIndex = 3;
+            buttonCancel.Text = "Закрыть";
+            buttonCancel.UseVisualStyleBackColor = true;
+            buttonCancel.Click += ButtonCancel_Click;
+            // 
+            // FormCheckTimeJoin
+            // 
+            AutoScaleDimensions = new SizeF(8F, 20F);
+            AutoScaleMode = AutoScaleMode.Font;
+            ClientSize = new Size(604, 259);
+            Controls.Add(buttonCancel);
+            Controls.Add(groupBoxSecond);
+            Controls.Add(groupBoxFirst);
+            Name = "FormCheckTimeJoin";
+            Text = "Замер времени сложных запросов";
+            groupBoxFirst.ResumeLayout(false);
+            groupBoxFirst.PerformLayout();
+            groupBoxSecond.ResumeLayout(false);
+            groupBoxSecond.PerformLayout();
+            ResumeLayout(false);
+        }
+
+        #endregion
+
+        private TextBox textBoxFirstCheck;
+        private GroupBox groupBoxFirst;
+        private Button buttonCheckFirstJoin;
+        private GroupBox groupBoxSecond;
+        private TextBox textBoxSecondCheck;
+        private Button buttonCheckSecondJoin;
+        private Button buttonCancel;
+    }
+}

TransportCompany/TransportCompany/FormCheckTimeJoin.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Data;
+using System.Drawing;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Forms;
+using TransportCompanyContracts.BusinessLogicsContracts;
+
+namespace TransportCompany
+{
+    public partial class FormCheckTimeJoin : Form
+    {
+        private readonly ITruckingLogic _truckingLogic;
+
+        private readonly IClientLogic _clientLogic;
+
+        public FormCheckTimeJoin(ITruckingLogic truckingLogic, IClientLogic clientLogic)
+        {
+            InitializeComponent();
+
+            _truckingLogic = truckingLogic;
+            _clientLogic = clientLogic;
+        }
+
+        private void ButtonCheckFirstJoin_Click(object sender, EventArgs e)
+        {
+            try
+            {
+                textBoxFirstCheck.Text = _truckingLogic.TestFirstJoin();
+            }
+            catch (Exception ex)
+            {
+                MessageBox.Show(ex.Message, "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Error);
+            }
+        }
+
+        private void ButtonCheckSecondJoin_Click(object sender, EventArgs e)
+        {
+            try
+            {
+                textBoxSecondCheck.Text = _clientLogic.TestSecondJoin();
+            }
+            catch (Exception ex)
+            {
+                MessageBox.Show(ex.Message, "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Error);
+            }
+        }
+
+        private void ButtonCancel_Click(object sender, EventArgs e)
+        {
+            DialogResult = DialogResult.Cancel;
+            Close();
+        }
+    }
+}

TransportCompany/TransportCompany/FormCheckTimeJoin.resx

@@ -0,0 +1,60 @@
+<root>
+  <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>

TransportCompany/TransportCompany/FormTrucking.Designer.cs

@@ -39,12 +39,13 @@
             rndGenerationToolStripMenuItem = new ToolStripMenuItem();
             generationClientsToolStripMenuItem = new ToolStripMenuItem();
             generationTruckingsToolStripMenuItem = new ToolStripMenuItem();
+            testTimeGetDataToolStripMenuItem = new ToolStripMenuItem();
             buttonUpdate = new Button();
             comboBoxEmails = new ComboBox();
             label1 = new Label();
             checkBoxSorted = new CheckBox();
             checkBoxForFilterMode = new CheckBox();
-            testTimeGetDataToolStripMenuItem = new ToolStripMenuItem();
+            testComplexQueriesToolStripMenuItem = new ToolStripMenuItem();
             ((System.ComponentModel.ISupportInitialize)dataGridView).BeginInit();
             menuStrip.SuspendLayout();
             SuspendLayout();
@@ -72,7 +73,7 @@
             // menuStrip
             // 
             menuStrip.ImageScalingSize = new Size(20, 20);
-            menuStrip.Items.AddRange(new ToolStripItem[] { toolStripMenuItem, rndGenerationToolStripMenuItem, testTimeGetDataToolStripMenuItem });
+            menuStrip.Items.AddRange(new ToolStripItem[] { toolStripMenuItem, rndGenerationToolStripMenuItem, testTimeGetDataToolStripMenuItem, testComplexQueriesToolStripMenuItem });
             menuStrip.Location = new Point(0, 0);
             menuStrip.Name = "menuStrip";
             menuStrip.Padding = new Padding(6, 3, 0, 3);
@@ -136,6 +137,13 @@
             generationTruckingsToolStripMenuItem.Text = "Генерация перевозок";
             generationTruckingsToolStripMenuItem.Click += GenerationTruckingsToolStripMenuItem_Click;
             // 
+            // testTimeGetDataToolStripMenuItem
+            // 
+            testTimeGetDataToolStripMenuItem.Name = "testTimeGetDataToolStripMenuItem";
+            testTimeGetDataToolStripMenuItem.Size = new Size(227, 24);
+            testTimeGetDataToolStripMenuItem.Text = "Тест скорости чтения данных";
+            testTimeGetDataToolStripMenuItem.Click += TestTimeGetDataToolStripMenuItem_Click;
+            // 
             // buttonUpdate
             // 
             buttonUpdate.Location = new Point(1014, 138);
@@ -185,12 +193,12 @@
             checkBoxForFilterMode.Text = "Включить режим фильтра";
             checkBoxForFilterMode.UseVisualStyleBackColor = true;
             // 
-            // testTimeGetDataToolStripMenuItem
+            // testComplexQueriesToolStripMenuItem
             // 
-            testTimeGetDataToolStripMenuItem.Name = "testTimeGetDataToolStripMenuItem";
+            testComplexQueriesToolStripMenuItem.Name = "testComplexQueriesToolStripMenuItem";
-            testTimeGetDataToolStripMenuItem.Size = new Size(227, 24);
+            testComplexQueriesToolStripMenuItem.Size = new Size(188, 24);
-            testTimeGetDataToolStripMenuItem.Text = "Тест скорости чтения данных";
+            testComplexQueriesToolStripMenuItem.Text = "Тест сложных запросов";
-            testTimeGetDataToolStripMenuItem.Click += TestTimeGetDataToolStripMenuItem_Click;
+            testComplexQueriesToolStripMenuItem.Click += TestComplexQueriesToolStripMenuItem_Click;
             // 
             // FormTrucking
             // 
@@ -248,5 +256,6 @@
         private CheckBox checkBoxSorted;
         private CheckBox checkBoxForFilterMode;
         private ToolStripMenuItem testTimeGetDataToolStripMenuItem;
+        private ToolStripMenuItem testComplexQueriesToolStripMenuItem;
     }
 }

TransportCompany/TransportCompany/FormTrucking.cs

@@ -176,5 +176,16 @@ namespace TransportCompany
                 LoadData();
             }
         }
+
+        private void TestComplexQueriesToolStripMenuItem_Click(object sender, EventArgs e)
+        {
+            var service = Program.ServiceProvider?.GetService(typeof(FormCheckTimeJoin));
+
+            if (service is FormCheckTimeJoin form)
+            {
+                form.ShowDialog();
+                LoadData();
+            }
+        }
     }
 }

TransportCompany/TransportCompany/Program.cs

@@ -62,6 +62,7 @@ namespace TransportCompany
 			services.AddTransient<FormRandomCreateClient>();
 			services.AddTransient<FormRandomCreateTrucking>();
 			services.AddTransient<FormTimeCheck>();
+			services.AddTransient<FormCheckTimeJoin>();
 		}
 	}
 }

TransportCompany/TransportCompanyBusinessLogic/BusinessLogic/ClientLogic.cs

@@ -80,12 +80,18 @@ namespace TransportCompanyBusinessLogic.BusinessLogic
 			return true;
 		}
 
-
+		//для замера времени рандомного добавления
         public string TestRandomCreate(int count, string[] _name, string[] _surname, string[] _patronymic, string[] _telephone, string[] _email)
         {
 			return _clientStorage.TestRandomInsert(count, _name, _surname, _patronymic, _telephone, _email);
         }
 
+        //для проверки времени выполнения сложного запроса
+        public string TestSecondJoin()
+        {
+            return _clientStorage.SecondJoin();
+        }
+
         public bool Update(ClientBindingModel model)
 		{
 			CheckModel(model);

TransportCompany/TransportCompanyBusinessLogic/BusinessLogic/TruckingLogic.cs

@@ -92,6 +92,12 @@ namespace TransportCompanyBusinessLogic.BusinessLogic
 			return _truckingStorage.TestRandomInsert(count, clients, cargos, transports, transportations);
         }
 
+		//первый сложный запрос
+        public string? TestFirstJoin()
+        {
+			return _truckingStorage.FirstJoin();
+        }
+
         public bool Update(TruckingBindingModel model)
 		{
 			CheckModel(model);

TransportCompany/TransportCompanyContracts/BusinessLogicsContracts/IClientLogic.cs

@@ -19,6 +19,8 @@ namespace TransportCompanyContracts.BusinessLogicsContracts
 
         string TestRandomCreate(int count, string[] _name, string[] _surname, string[] _patronymic, string[] _telephone, string[] _email);
 
+		string TestSecondJoin();
+
         bool Update(ClientBindingModel model);
 
 		bool Delete(ClientBindingModel model);

TransportCompany/TransportCompanyContracts/BusinessLogicsContracts/ITruckingLogic.cs

@@ -15,6 +15,8 @@ namespace TransportCompanyContracts.BusinessLogicsContracts
 
         string? TestReadList();
 
+		string? TestFirstJoin();
+
         TruckingViewModel? ReadElement(TruckingSearchModel model);
 
 		bool Create(TruckingBindingModel model);

TransportCompany/TransportCompanyContracts/StoragesContracts/IClientStorage.cs

@@ -21,6 +21,8 @@ namespace TransportCompanyContracts.StoragesContracts
 
         string TestRandomInsert(int count, string[] _name, string[] _surname, string[] _patronymic, string[] _telephone, string[] _email);
 
+		string SecondJoin();
+
         ClientViewModel? Update(ClientBindingModel model);
 
 		ClientViewModel? Delete(ClientBindingModel model);

TransportCompany/TransportCompanyContracts/StoragesContracts/ITruckingStorage.cs

@@ -15,6 +15,8 @@ namespace TransportCompanyContracts.StoragesContracts
 
 		string TestGetFullList();
 
+        string FirstJoin();
+
         List<TruckingViewModel> GetFilteredList(TruckingSearchModel model);
 
 		TruckingViewModel? GetElement(TruckingSearchModel model);

TransportCompany/TransportCompanyDatabaseImplements/Implements/ClientStorage.cs

@@ -111,6 +111,46 @@ namespace TransportCompanyDatabaseImplements.Implements
             return stopwatch.ElapsedMilliseconds.ToString();
         }
 
+
+        public string SecondJoin()
+        {
+            using var context = new ElegevContext();
+
+            Random rnd = new Random(DateTime.Now.ToString().GetHashCode());
+
+            //старт замера времени добавления в бд
+            Stopwatch stopwatch = new();
+
+            stopwatch.Start();
+
+            var secondJoin = from t in context.Set<Trucking>()
+						from c in context.Set<Client>().Where(c => c.Id == t.ClientId)
+                        select new { c, t };
+
+            //ВСЁ ГОТОВО ДЛЯ СЛЕДУЮЩЕГО ЗАМЕРА
+
+            foreach (var element in secondJoin)
+            {
+                element.t.Update(new TruckingBindingModel
+                {
+                    Id = element.t.Id,
+                    ClientId = element.t.ClientId,
+                    CargoId = element.t.CargoId,
+                    Price = element.t.Price,
+                    DateStart = element.t.DateStart.AddDays(-10),
+                    DateEnd = element.t.DateEnd.AddDays(-10),
+                    TransportationId = element.t.TransportationId,
+                    TransportId = element.t.TransportId,
+                });
+            }
+
+            context.SaveChanges();
+
+            stopwatch.Stop();
+
+            return stopwatch.ElapsedMilliseconds.ToString();
+        }
+
         public ClientViewModel? Update(ClientBindingModel model)
 		{
 			using var context = new ElegevContext();

TransportCompany/TransportCompanyDatabaseImplements/Implements/TruckingStorage.cs

@@ -198,5 +198,46 @@ namespace TransportCompanyDatabaseImplements.Implements
 				throw;
 			}
 		}
+
+		//первый сложный запрос
+		public string FirstJoin()
+		{
+            using var context = new ElegevContext();
+
+            Random rnd = new Random(DateTime.Now.ToString().GetHashCode());
+
+            //старт замера времени добавления в бд
+            Stopwatch stopwatch = new();
+
+            stopwatch.Start();
+
+			var firstJoin = from t in context.Set<Trucking>().Where(t => t.Price == 1200000.0)
+							from c in context.Set<Client>().Where(c => c.Id == t.ClientId)
+							select new { t, c };
+
+			//ВСЁ ГОТОВО ДЛЯ СЛЕДУЮЩЕГО ЗАМЕРА
+            // 999999.0
+
+            foreach (var element in firstJoin)
+			{
+				element.t.Update(new TruckingBindingModel
+				{
+                    Id = element.t.Id,
+					ClientId = element.t.ClientId,
+					CargoId = element.t.CargoId,
+					Price = 999999.0,
+					DateStart = element.t.DateStart,
+					DateEnd = element.t.DateEnd,
+					TransportationId = element.t.TransportationId,
+					TransportId = element.t.TransportId,
+				});
+			}
+
+			context.SaveChanges();
+
+            stopwatch.Stop();
+
+            return stopwatch.ElapsedMilliseconds.ToString();
+        }
 	}
 }