如何在WPF中获取折叠控件的宽度/高度？

Question

im wondering if theres an easy way to get the width of a control in WPF at runtime while the control is collapsed.

when i use control.Width ill get the following result: -1.#IND and control.actualWidth will return 0.0 because its collapsed.

i want to resize my window and then display the collapsed control.

thanks

Edit:
Some details

i have a grid with 2 columns in my window, the 1st column holds a tab control, the 2nd column holds an expander control. i want to extend the width of my window when expanding the expander control, so the content in the 1st column will remain its size.

Answer 1

Put the control in question inside a container (like a ContentControl ) and collapse the container rather than the control itself. Then you should be able to simply call Measure (or use the DesiredSize property) on the control to determine how much room it wants.

Answer 2

You have to call the UpdateLayout method on the control or conainer of control. After that the things may work properly.

Answer 3

In UWP you can determine size of collapsed control by making it visible for a sec and then hiding it again, change is not noticeable:

var oldVisibility = myBorder.Visibility;
myBorder.Visibility = Visibility.Visible;
myBorder.UpdateLayout();
var height = myBorder.RenderSize.Height;
myBorder.Visibility = oldVisibility;

Answer 4

Post which is marked as an answer actually does not answer the question, it just gives a workaround.

To get the size of the collapsed control you need:

1. Set control's visibility as Hidden (Collapsed won't evaluate).
2. Call Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity)) method of the control.
3. Get the size from DesiredSize property of the control.
4. Then you can Collapse your control back.

Answer 5

What size do you expect to get?

The size is not just dependent on the control but also on its container. So the actual size can not be determined unless the control is actually rendered.

Instead of using Collapsed you could make it Invisible that way it will be sized by its own logic and the logic of the container.

EDIT

In the comments it became clear that what the reason was for needing the size of the control:

I have a grid with 2 columns in my window, the 1st column holds a tab control, the 2nd column a holds an expander control. i want to extend the width of my window when expanding the expander control, so the content in the 1st column will remain its size.

My answer:

Set the SizeToContent of the window to WidthAndHeight and set the width of both grid columns to auto. That should take care of it.

Answer 6

I believe you're going about this the wrong way. You can set the Window Width and height to "Auto" and then it will take care of all the resizing stuff.

The problem arises whenever you directly set the Width property of any control(trust me I've done it). Once you do that, you've told WPF hands off of resizing logic, I know what I'm doing.

If you think something isn't resizing at the right time you can add a handler to some event and then call control.InvalidateVisual() or control.InvalidateMeasurement() which will make it go through a whole new layout pass.