Compiler Error CS0445

Cannot modify the result of an unboxing conversion

The result of an unboxing conversion is a temporary variable. The compiler prevents you from modifying such variables because any modification would go away when the temporary variable goes away. To fix this, declare a new value-type variable to store the intermediate expression, and assign the result of the unboxing conversion to that variable.

The following code generates CS0455.

// CS0445.CS  
class UnboxingTest  
{  
    public static void Main()  
    {  
        Point p;  
        p.x = 1;  
        p.y = 2;  
        object obj = p;  
        // The following line generates CS0445, because the result  
        // of unboxing obj is a temporary variable.  
        ((Point)obj).x = 2;  

        // The following lines resolve the error.  

        // Store the result of the unboxing conversion in p2.  
        Point p2;       
        p2 = (Point)obj;  
        // Then you can modify the unboxed value.  
        p2.x = 2;  
    }  
}  

struct Point  
{  
    public int x, y;  
}