Events....

CustomComponents/DropList.Designer.cs

@@ -39,6 +39,7 @@
             listBox.Name = "listBox";
             listBox.Size = new Size(150, 104);
             listBox.TabIndex = 0;
+            listBox.SelectedValueChanged += 
             // 
             // Frame
             // 

CustomComponents/DropList.cs

@@ -3,7 +3,22 @@
     public partial class Frame : UserControl
     {
 
+        private event EventHandler? _valueChanged;
+
         private string? SelectedValue = string.Empty;
+
+        public event EventHandler ValueChanged
+        {
+            add
+            {
+                _valueChanged += value;
+            }
+            remove
+            {
+                _valueChanged -= value;
+            }
+        }
+
         public Frame()
         {
             InitializeComponent();
@@ -21,7 +36,6 @@
         public void Clear()
         {
             listBox.Items.Clear();
-
         }
 
         public string? Value
@@ -36,9 +50,11 @@
             }
         }
 
-        private void ValueChanged(object sender, EventArgs e)
+        private void SelectedValue_Changed(object sender, EventArgs e)
         {
-            Value = listBox.SelectedItem.ToString();
+            var element = sender as ListBox;
+            Value = element.Text.ToString();
+            _valueChanged?.Invoke(this, e);
         }
     }
 }

TestForms/Form1.cs

@@ -2,9 +2,11 @@ namespace TestForms
 {
     public partial class TestFrame : Form
     {
+        
         public TestFrame()
         {
             InitializeComponent();
+            listBox.ValueChanged += new EventHandler()
         }
 
         private void clearButton_Click(object sender, EventArgs e)
@@ -15,7 +17,10 @@ namespace TestForms
         private void fillButton_Click(object sender, EventArgs e)
         {
             listBox.PopulateList(new List<string> { "SILENT", "RIZZ", "BLSSDY", "YUEEJKE" });
+            
         }
 
+        
+
     }
 }