C# .NET

The Leave Event In C# .Net

 

 

A very useful event you can use for text boxes is the Leave event. It allows
you to validate a text box when a user tries to leave it. You can check, for
example, if the text box is blank. If it needs to be filled in, you can keep
them there. Let’s try that.

Add two text boxes to your form. Locate the TabIndex property for textbox1
and set it to 0. For textbox2, set the TabIndex property to 1.

The TabIndex property refers to which control will be selected when the Tab
key is pressed. On a form that a user has to fill in, you want the cursor to
jump to the next textbox. You don’t want the cursor jumping down from textbox1
to textbox8 – it has to be a nice sequential order. The TabIndex allows you
to set the Tab order for all the controls on your form.

With TextBox1 selected, click the lightning bolt in the properties area to
see a list of events for textboxes. You should see this:

C# Properties box for the Leave Event

Double click the Leave event to bring up its code stub. Now enter the following
code:

C# code for a Leave Event

The code just checks for a blank text box. But it makes the check when the
user attempts to leave the text box and move on to the next one. Notice how
the user is brought back to the text box:

textBox1.Focus( );

The Focus method can be used to force a control to be selected. For text boxes,
this means that the cursor will be flashing inside of it.

You can also do things like converting text to upper or proper case when the
users Tabs away from a text box. Here’s some code that converts to uppercase:

C# code to detect if a text box is blank

In the next part, we’ll take a look at Events for ListBoxes and ComboBoxes.

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Kaynak : https://www.homeandlearn.co.uk/csharp/csharp_s9p4.html ‘sitesinden alıntı

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