This tutorial was created with Microsoft's LINQ Community Technology Preview release, which can be downloaded from here
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In this introduction, we will introduce you to using LINQ in a Windows Form to find all controls on the form of a certain type, and then interact with them by disabling them. In the example, we will have three textboxes, a button to disable them all and a button to enable them all.
The first thing we do after installing the LINQ release above, is to start a new project > Visual Basic LINQ Windows Application.
We will start by adding the controls to the form. In this example, we will have a total of 5 buttons, and three textboxes.
The form should look something like this:
Now we have our form, we can add the logic to the code-behind. Under the Disable Button click event we add the following:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
For Each myChildTextBox As TextBox In Me.Controls.OfType(Of TextBox)()
myChildTextBox.Enabled = False
Next myChildTextBox |
This code searches for all controls on the page that are TextBoxes, then it loops through all of them, disabling them one by one.
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We can also add logic to the Enable Button, and also to buttons to disable and enable each individual button, but we don't need to use LINQ for those. The code-behind will look something like this:
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
For Each myChildTextBox As TextBox In Me.Controls.OfType(Of TextBox)()
myChildTextBox.Enabled = False
Next myChildTextBox
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
For Each myChildTextBox As TextBox In Me.Controls.OfType(Of TextBox)()
myChildTextBox.Enabled = True
Next myChildTextBox
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
If TextBox1.Enabled = True Then
TextBox1.Enabled = False
Button3.Text = "Enable >>"
Else
TextBox1.Enabled = True
Button3.Text = "Disable >>"
End If
End Sub
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
If TextBox2.Enabled = True Then
TextBox2.Enabled = False
Button4.Text = "Enable >>"
Else
TextBox2.Enabled = True
Button4.Text = "Disable >>"
End If
End Sub
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
If TextBox3.Enabled = True Then
TextBox3.Enabled = False
Button5.Text = "Enable >>"
Else
TextBox3.Enabled = True
Button5.Text = "Disable >>"
End If
End Sub |
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