ECMA-334 C# Language Specification

17.5.8: Method body

The method-body of a method declaration consists of either a block or a semicolon.

Abstract and external method declarations do not provide a method implementation, so their method bodies simply consist of a semicolon. For any other method, the method body is a block (15.2) that contains the statements to execute when that method is invoked.

When the return type of a method is void , return statements (15.9.4) in that method's body are not permitted to specify an expression. If execution of the method body of a void method completes normally (that is, control flows off the end of the method body), that method simply returns to its caller.

When the return type of a method is not void , each return statement in that method body must specify an expression of a type that is implicitly convertible to the return type. The endpoint of the method body of a value-returning method must not be reachable. In other words, in a value-returning method, control is not permitted to flow off the end of the method body.

[Example: In the example 
class A  
{  
   public int F() {}     // Error, return value required  
   public int G() {  
      return 1;  
   }  
   public int H(bool b) {  
      if (b) {  
         return 1;  
      }  
      else {  
         return 0;  
      }  
   }  
}
the value-returning F method results in a compile-time error because control can flow off the end of the method body. The G and H methods are correct because all possible execution paths end in a return statement that specifies a return value. end example]