#268 – You Must Set the Value of All out Parameters Before Returning from a Method

You can use out parameters as a way of returning multiple data values from a method to its caller.  Because the intention of an output parameter is to return data to the caller, you must assign some value to every parameter marked as out before you can return from a method.  The compiler will enforce this rule.

In the example below, we’ve failed to set a value for the barkPhrase output parameter.

        public void GetDogVitals(out string fullName, out int age, out string barkPhrase)
            fullName = string.Format("{0}, {1}", Name, Title);
            age = Age;
            //barkPhrase = BarkPhrase;

When we try to compile the code, we’ll get an error telling us that we must assign a value to the barkPhrase output parameter before control leaves the method.