OUT Parameter

OUT parameters are parameters which are passed back from a function to the calling function or method, it is good enough to declare the parameters in the calling method they need not be initialized in the calling class, instead their values will be assigned in the function which is returning the out parameters.

OUT parameters are declared similar to the normal parameters by adding an out keyword in front of the parameter as follows.

public int GetEmployeeDetails(out string empName)

OUT parameters come in handy when we need to return more than one value from a function, functions can always return only one value, OUT parameters help in overcoming this limitations by allowing us to pass additional values from a function.

In the following class we will pass the employee name as an OUT parameter to the function GetEmployeeDetails.

    class CEmployee

    {

        int nId;

        string sName;

        //

        public CEmployee(int id, string name)

        {

            nId = id;

            sName = name;

        }

        //

        public int GetEmployeeDetails(out string empName)

        {

            empName = sName;

            return nId;

        }

    }

The code to call this function is as follows.

    string employeeName;

    CEmployee objEmployee = new CEmployee(1, "Name1");

    //

    int empID = objEmployee.GetEmployeeDetails(out employeeName);

    Console.WriteLine("EMP ID: " + empID.ToString());

    Console.WriteLine("EMP Name: " + employeeName);

Notice that the out parameter employeeName is just declared in the calling function and the actual value assignment to the parameter happens in the the GetEmployeeDetails method of the called function. Even if we try to assign some value to the parameter variable in the calling function it will be overwritten by the called function.