Check all yellow checkboxes

**rythmic** · Dec 11 '10, 01:57 AM

How about putting all checkboxes in an array and then iterate through that array.

I actually don't know VB syntax at all but i do know C# and that approach would work fine.

Since I don't know VB syntax I can't help you there but a conceptual solution would be this:

Code:

Dim cbs As CheckBox[] = {All checkboxes here}
Dim allYellowStatus As bool = Allyellow.Checked; 
For Each checkBox As CheckBox In cbs {
    If checkBox.BackColor = Color.LightYellow Then
        checkBox.Checked = allYellowStatus
    End If
}

Something like that seems a bit easier to grasp.

**Joseph Martell** · Dec 13 '10, 04:44 AM

There is actually a better way to do this. Your controls on your form are already in a collection. What you need is an efficient way to get all check boxes that have the light yellow background.

IF you are using .Net framework 3.5 or greater then you have access to a couple of extension methods that can make life a little easier for you.

Here is a complete code sample that should work:

Code:

Dim lightYellowCheckBoxes As List(Of CheckBox) = Nothing

lightYellowCheckBoxes = Me.Controls.OfType(Of CheckBox).Where(Function(chkBox As CheckBox) chkBox.BackColor = Color.LightYellow)

If (AllYellow.Checked) Then

    For Each chkBox In lightYellowCheckBoxes
        chkBox.Checked = True
    Next
Else
    For Each chkBox In lightYellowCheckBoxes
        chkBox.Checked = False
    Next
End If

The key to this code is the following line:

Code:

lightYellowCheckBoxes = Me.Controls.OfType(Of CheckBox).Where(Function(chkBox As CheckBox) chkBox.BackColor = Color.LightYellow)

This is kind of complicated, especially if you've never seen it before (and the VB syntax makes this a little bit less clear, in my opinion). Lets break it down:

lightYellowChec kBoxes is a list(of CheckBox) so it holds a collection of checkboxes. Because of the way that this is implemented it dynamically sizes itself to hold as many check boxes as you need. This means you don't have to worry about sizing your array correctly, or manually resizing your array during processing.

Me.Controls references the collection of controls that are currently on the window. The .Net framework 3.5 introduces the extension method OfType:

Code:

Me.Controls.OfType(Of CheckBox)

This statement returns a collection of all the check box controls in the Me.Controls collection.

Finally, the .Where extension method is also introduced in .Net framework 3.5. So, with Me.Controls.OfT ype(Of CheckBox) we accessed a collection of check boxes on the form. Using the .Where extension allows to return another collection of controls. Unlike .OfType, which just filters on the type of the control, we get to supply a predicate of the .Where extension ourselves.

From the statement:

Code:

lightYellowCheckBoxes = Me.Controls.OfType(Of CheckBox).Where(Function(chkBox As CheckBox) chkBox.BackColor = Color.LightYellow)

the predicate is provided by this part of the code:

Code:

Function(chkBox As CheckBox) chkBox.BackColor = Color.LightYellow

This statement creates a Lambda function. Think of a Lambda function as a single-purpose, unnamed function that we create on-the-fly and use for a very specific reason. In this case, I am creating a function that takes a check box and returns a boolean value based on whether the background of that check box was Color.LightYell ow. The return type is implied.

Now lightYellowChec kBoxes references a list of checkboxes on the current form with a background of light yellow.

This code can be made more efficient if the check boxes with light yellow backgrounds do not change. You could make lightYellowChec kBoxes a private class member (instead of a local collection in the function) and put:

Code:

lightYellowCheckBoxes = Me.Controls.OfType(Of CheckBox).Where(Function(chkBox As CheckBox) chkBox.BackColor = Color.LightYellow)

in your form load event. That way you are only creating your list of check boxes once.

The if statements and loops are pretty self explanatory. I chose to nest the for loops inside the if statements because that way your code would perform one conditional test and then fall into a loop. Nesting the if statement inside the loop would mean that the conditional test occurs in each iteration of the loop. Just a side note.

You should also know that everything that was achieved with the .OfType and .Where extension methods can be achieved with other code as well. .OfType and .Where are just meant to be syntactic sugar to make life easier for you.

Check all yellow checkboxes

Check all yellow checkboxes

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