сдано

COP/VisualComponentsLib/MyDropDownList.cs

@@ -52,10 +52,23 @@ namespace VisualComponentsLib
 				}
 			}
 		}
+
+		private EventHandler onValueChanged;
+		public event EventHandler ValueChanged
+		{
+			add
+			{
+				onValueChanged += value;
+			}
+			remove
+			{
+				onValueChanged -= value;
+			}
+		}
+
 		private void comboBox_SelectedValueChanged(object sender, EventArgs e)
 		{
-			if (dropDownList.BackColor == Color.LightGreen) dropDownList.BackColor = Color.Tomato;
-			else dropDownList.BackColor = Color.LightGreen;
+			onValueChanged?.Invoke(sender, e);
 		}
 	}
 }

COP/VisualComponentsLib/MyEmailTextBox.cs

@@ -33,7 +33,8 @@ namespace VisualComponentsLib
 				}
 				else
 				{
-					throw new Exception("Неправильный адрес");
+					Error = "Некорректный ввод";
+					return null;
 				}
 			}
 			set
@@ -46,10 +47,14 @@ namespace VisualComponentsLib
 				}
 				else
 				{
-					throw new Exception("Неправильный адрес");
+					Error = "Некорректный ввод";
 				}
 			}
 		}
+		public string Error
+		{
+			get; private set;
+		}
 		public void setExample(string str)
 		{
 			Regex rg = new Regex(Pattern);
@@ -63,23 +68,26 @@ namespace VisualComponentsLib
 		private void textBox_Enter(object sender, EventArgs e)
 		{
 			int VisibleTime = 2000;  //ms
-
 			ToolTip tooltip = new ToolTip();
 			tooltip.Show(example, emailTextBox, 30, -20, VisibleTime);
 		}
 
+		private EventHandler onValueChanged;
+		public event EventHandler ValueChanged
+		{
+			add
+			{
+				onValueChanged += value;
+			}
+			remove
+			{
+				onValueChanged -= value;
+			}
+		}
+
 		private void textBox_TextChanged(object sender, EventArgs e)
 		{
-			Regex rg = new Regex(Pattern);
-			bool address = rg.IsMatch(emailTextBox.Text);
-			if (address)
-			{
-				emailTextBox.BackColor = Color.Green;
-			}
-			else
-			{
-				emailTextBox.BackColor = Color.Red;
-			}
+			onValueChanged?.Invoke(sender, e);
 		}
 	}
 }

COP/WinForms/FormForComponents.Designer.cs

@@ -1,6 +1,6 @@
 namespace WinForms
 {
-	partial class Form1
+	partial class FormForComponents
 	{
 		/// <summary>
 		///  Required designer variable.

COP/WinForms/FormForComponents.cs

@@ -1,13 +1,12 @@
-using System.Security.Cryptography;
 using VisualComponentsLib.Object;
 
 namespace WinForms
 {
-	public partial class Form1 : Form
+	public partial class FormForComponents : Form
 	{
 		List<string> list = new List<string>();
 		List<Student> students = new List<Student>();
-		public Form1()
+		public FormForComponents()
 		{
 			list = new List<string>();
 			list.AddRange(new string[] { "õëåá", "ìîëîêî", "êîëáàñà" });
@@ -21,6 +20,11 @@ namespace WinForms
 			dropDownList.LoadValues(new List<string>() { "ñîê", "ÿáëîêî", "ëóê" });
 			emailTextBox.Pattern = @"^([\w\.\-]+)@([\w\-]+)((\.(\w){2,3})+)$";
 			listBoxObj.SetLayoutInfo("Ôàìèëèÿ *Name* Ãðóïïà *Group* Ôàêóëüòåò *Faculty* Êóðñ *Course*", "*", "*");
+			dropDownList.ValueChanged += CustomEventHandler;
+		}
+		private void CustomEventHandler(object sender, EventArgs e)
+		{
+			MessageBox.Show("Âûáðàííûé ýëåìåíò èçìåíåí");
 		}
 		private void buttonAdd_Click(object sender, EventArgs e)
 		{

COP/WinForms/Program.cs

@@ -11,7 +11,7 @@ namespace WinForms
 			// To customize application configuration such as set high DPI settings or default font,
 			// see https://aka.ms/applicationconfiguration.
 			ApplicationConfiguration.Initialize();
-			Application.Run(new Form1());
+			Application.Run(new FormForComponents());
 		}
 	}
 }