How to Create a Custom Control

namespace ControlsDemo
{
public class ExtdTextBox : TextBox
{
#region Member Variables
Color waterMarkColor = Color.Gray;
Color forecolor;
Font font;
Font waterMarkFont;
string waterMarkText = "Your Text Here";
#endregion
#region Constructor
public ExtdTextBox()
{
base.Text = this.waterMarkText;
this.forecolor = this.ForeColor;
this.ForeColor = this.waterMarkColor;
this.font = this.Font;
//event handlers
this.TextChanged += new EventHandler(ExtdTextBox_TextChanged);
this.KeyPress += new KeyPressEventHandler(ExtdTextBox_KeyPress);
this.LostFocus += new EventHandler(ExtdTextBox_TextChanged);
}
#endregion
#region Event Handler Methods
void ExtdTextBox_TextChanged(object sender, EventArgs e)
{
if (!string.IsNullOrEmpty(this.Text))
{
this.ForeColor = this.forecolor;
this.Font = this.font;
}
else
{
this.TextChanged -= new EventHandler(ExtdTextBox_TextChanged);
base.Text = this.waterMarkText;
this.TextChanged += new EventHandler(ExtdTextBox_TextChanged);
this.ForeColor = this.waterMarkColor;
this.Font = this.waterMarkFont;
}
}|
void ExtdTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
string str = base.Text.Replace(this.waterMarkText, "");
this.TextChanged -= new EventHandler(ExtdTextBox_TextChanged);
this.Text = str;
this.TextChanged += new EventHandler(ExtdTextBox_TextChanged);
}
#endregion
#region User Defined Properties
/// <summary>
/// Property to set/get Watermark color at design/runtime
/// </summary>
[Browsable(true)]
[Category("Extended Properties")]
[Description("sets Watermark color")]
[DisplayName("WaterMark Color")]
public Color WaterMarkColor
{
get
{
return this.waterMarkColor;
}
set
{
this.waterMarkColor = value;
base.OnTextChanged(new EventArgs());
}
}
[Browsable(true)]
[Category("Extended Properties")]
[Description("sets TextBox text")]
[DisplayName("Text")]
/// <summary>
/// Property to get Text at runtime(hides base Text property)
/// </summary>
public new string Text
{
get
{
//required for validation for Text property
return base.Text.Replace(this.waterMarkText, string.Empty);
}
set
{
base.Text = value;
}
}
[Browsable(true)]
[Category("Extended Properties")]
[Description("sets WaterMark font")]
[DisplayName("WaterMark Font")]
/// <summary>
/// Property to get Text at runtime(hides base Text property)
/// </summary>
public Font WaterMarkFont
{
get
{
//required for validation for Text property
return this.waterMarkFont;
}
set
{
this.waterMarkFont = value;
this.OnTextChanged(new EventArgs());
}
}
/// <summary>
/// Property to set/get Watermark text at design/runtime
/// </summary>
[Browsable(true)]
[Category("Extended Properties")]
[Description("sets Watermark Text")]
[DisplayName("WaterMark Text")]
public string WaterMarkText
{
get
{
return this.waterMarkText;
}
set
{
this.waterMarkText = value;
base.OnTextChanged(new EventArgs());
}
}
#endregion
}
}

The other optional attributes declaration names are self-explanatory.

5) Build the project and refer to the dll in another Windows Forms project.

Right-click on the ToolBar Window and click ChooseItems:

Click on browse and select control dll:

Click ok:

Drag and drop the control onto the form: