Hi you can use this example,
Program - Checking for validity of an expression
using System;
class CheckExpression
{
public static void Main()
{
int x,y,a,b;
x - y = 100;
// gives error
//"The left-hand side of an assignment must be a variable, property or
indexer"
x - (y = 100);
// gives error
//"Only assignment, call, increment, decrement, and new object expressions
// can be used as a statement"
}
}