Сделано по образцу из лекции

Trolleybus/Trolleybus/FormTrolleybusConfig.cs

@@ -13,6 +13,7 @@ namespace Trolleybus
     public partial class FormTrolleybusConfig : Form
     {
         DrawingTrolleybus _trolleybus = null;
+        private event TrolleybusDelegate EventAddTrolleybus;
         public FormTrolleybusConfig()
         {
             InitializeComponent();
@@ -27,6 +28,18 @@ namespace Trolleybus
             pictureBoxObject.Image = btm;
         }
 
+        public void AddEvent(TrolleybusDelegate ev)
+        {
+            if (EventAddTrolleybus == null)
+            {
+                EventAddTrolleybus = new TrolleybusDelegate(ev);
+            }
+            else
+            {
+                EventAddTrolleybus += ev;
+            }
+        }
+
         private void groupBox2_Enter(object sender, EventArgs e)
         {
 
@@ -37,7 +50,7 @@ namespace Trolleybus
             (sender as Label).DoDragDrop((sender as Label).Name, DragDropEffects.Move | DragDropEffects.Copy);
         }
 
-        private void panelObject_DragDrop(object sender, DragEventArgs e)
+        private void panelObject_DragEnter(object sender, DragEventArgs e)
         {
             if (e.Data.GetDataPresent(DataFormats.Text))
             {
@@ -49,7 +62,7 @@ namespace Trolleybus
             }
         }
 
-        private void panelObject_DragEnter(object sender, DragEventArgs e)
+        private void panelObject_DragDrop(object sender, DragEventArgs e)
         {
             switch (e.Data.GetData(DataFormats.Text).ToString())
             {
@@ -63,5 +76,10 @@ namespace Trolleybus
             }
             DrawTrolleybus();
         }
+        private void ButtonOk_Click(object sender, EventArgs e)
+        {
+            EventAddTrolleybus?.Invoke(_trolleybus);
+            Close();
+        }
     }
 }

Trolleybus/Trolleybus/Trolleybus.csproj

@@ -87,6 +87,7 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="SetTrolleybusGeneric.cs" />
     <Compile Include="SimpleMap.cs" />
+    <Compile Include="TrolleybusDelegate.cs" />
     <EmbeddedResource Include="Form1.resx">
       <DependentUpon>Form1.cs</DependentUpon>
     </EmbeddedResource>

Trolleybus/Trolleybus/TrolleybusDelegate.cs

@@ -0,0 +1,10 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Trolleybus
+{
+    public delegate void TrolleybusDelegate(DrawingTrolleybus trolleybus);
+}