public class class1
        { 
          const int valu11 = 5;   // Declared a Const and assigned a value to it
        }

        public class class1
        { 
          const int valu11 = 5;
          public class1           // Constructor
          {
             value1 = 10;  // Error  
          }
        }

public class class1
      { 
       readonly int valu11 = 5;// Declared a readonly and assigned a value to it
      }

        public class class1
        { 
          readonly int valu11 = 5;
          public class1           // Constructor
          {
             value1 = 10; // Allowed
          }
          public void method1()
          {
              value1 = 15  // Error
          }
        }