Custom TextBox Controls for WPF That Contains Null Text

Introduction

In this blog I have created a water mark TextBox using base control, I took custom control project and did some modification on the base control.

To make a water mark user control follow the following steps given bellow

Create new console control project
name the project name as you want to name the controls.
Add a class and rename that as per-requirement
Inherit that class from TextBoxclass

In this article I have named the control as MyTextBox, declare a public string property as NullText and set the value to 'Null Text'.

Code

public string _NullText = "Null Text";

public stringNullText {

get

{

return _NullText;

}

set

{

_NullText = value;

}

}

In the initialized event set the font color to gray and text to NullText if the textbox contains only nulltext, if not contains set the font color to black.

Code

if (string.IsNullOrEmpty(this.Text))

{

this.Text = NullText;

this.Foreground = Brushes.LightGray;

}

In the gotfucuse event clear the text of text box if it contains text same as nulltext and set the fore color to gray, if not fore color will be black. See the following code written bellow:

Code

if (this.Text == NullText)

{

this.Clear();

this.Foreground = Brushes.LightGray;

}

else

this.Foreground = Brushes.Black;

In the lost focuse event if the text box text is equals to nulltext then set the fore color to gray and if the text is equal to empty thatn set the text to nulltext other wise set the color to black

See the following code :

Code

private void MyTextBox_LostFocus(object sender, RoutedEventArgs e)

{

this.Text = (this.Text == string.Empty ? NullText : this.Text);

if (this.Text != NullText)

{

this.Foreground = Brushes.Black;

}

else

this.Foreground = Brushes.LightGray;

}

Full Code

public class MyTextBox : TextBox

{

public string _NullText = "Null Text";

public stringNullText {

get

{

return _NullText;

}

set

{

_NullText = value;

}

public MyTextBox()

{

this.GotFocus += new RoutedEventHandler(MyTextBox_GotFocus);

this.LostFocus += new RoutedEventHandler(MyTextBox_LostFocus);

this.TextChanged += new TextChangedEventHandler(MyTextBox_TextChanged);

this.Initialized += new EventHandler(MyTextBox_Initialized);

this.KeyDown+=new KeyEventHandler(MyTextBox_KeyDown);

}

void MyTextBox_Initialized(object sender, EventArgs e)

{

if (string.IsNullOrEmpty(this.Text))

{

this.Text = NullText;

this.Foreground = Brushes.LightGray;

}

void MyTextBox_KeyDown(object sender, KeyEventArgs e)

{

if (string.IsNullOrEmpty(this.Text))

{

this.Text = NullText;

}

e.Handled = false;

}

void MyTextBox_TextChanged(object sender, TextChangedEventArgs e)

{

if (this.Text != NullText)

{

this.Foreground = Brushes.Black;

}

private void MyTextBox_GotFocus(object sender, RoutedEventArgs e)

{

if (this.Text == NullText)

{

this.Clear();

this.Foreground = Brushes.LightGray;

}

else

this.Foreground = Brushes.Black;

}

private void MyTextBox_LostFocus(object sender, RoutedEventArgs e)

{

this.Text = (this.Text == string.Empty ? NullText : this.Text);

if (this.Text != NullText)

{

this.Foreground = Brushes.Black;

}

else

this.Foreground = Brushes.LightGray;

}