Projektdateien hinzufügen.

WindowsFormsApp1/Test/ExtendedTB.cs

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+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.ComponentModel;
+
+namespace WindowsFormsApp1.Test
+{
+    public class ExtendedTB : BaseTextBox
+    {
+        public ExtendedTB() : base()
+        {
+            ForeColor = Color.White;
+            BackColor = Color.Red;
+        }
+
+        public override void Reset()
+        {
+            base.Reset();
+            Text = "Resetted!";
+        }
+
+        [DefaultValue(typeof(Color), "Red")]
+        public Color BackColor
+        {
+            get { return base.BackColor; }
+            set { base.BackColor = value; }
+        }
+
+        public override string Description { get => base.Description; set => base.Description = value; }
+    }
+}