ArcGIS Pro 2.7 API Reference Guide
SetWidth Method (Element)
Example 

ArcGIS.Desktop.Layouts Namespace > Element Class : SetWidth Method
Double
Sets the width of the element. This method must be called on the MCT. Use QueuedTask.Run.
Syntax
public void SetWidth( 
   double width
)
Public Sub SetWidth( _
   ByVal width As Double _
) 

Parameters

width
Double
Exceptions
ExceptionDescription
This method must be called within the lambda passed to QueuedTask.Run.
This element requires its mapview to be active
Remarks
Placement for an element contained in graphics layer requires the mapview be active
Example
//Modify an element's width.

//Perform on the worker thread
await QueuedTask.Run(() =>
{
  double elmWidth = element.GetWidth();
  elmWidth = 8.5;

  element.SetWidth(elmWidth); //You don't have to get to set; a shortcut would be: element.SetWidth(8.5);
});
Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

Element Class
Element Members