using System; 
using System.Drawing ; 
using System.Collections .Generic ; 
 
public class Test
{ 
	public static  void  Main( )  { 
		var list =  new List< Point> ( ) ; 
		list.Add ( new Point( 10 ,  20 ) ) ; 
		list.Add ( new Point( 20 ,  40 ) ) ; 
		list.Add ( new Point( 40 ,  80 ) ) ; 
 
		list[ 1 ] .X  =  30 ; 
 
		foreach( var pt in list)  { 
			Console.WriteLine ( pt) ; 
		} 
 
	} 
} 
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	prog.cs(13,11): error CS1612: Cannot modify a value type return value of `System.Collections.Generic.List<System.Drawing.Point>.this[int]'. Consider storing the value in a temporary variable
Compilation failed: 1 error(s), 0 warnings