multiple out parameters with a return

Question

I have a method declaration like this:

public int myMethod(int x, out int y, out int z)
{
    int k;
    foreach(int i in someList)
    {
        if(anotherMethod(out k))
        {
            z = k;
        }
        else
        {
            z = 0;
        }
    }

    y = someValue;

    return anotherValue;
}

but I get this compiling error

The out parameter 'z' must be assigned to before control leaves the current method

Answer 1

If someList is empty, it will never enter the foreach loop, and therefore z will never be assigned. To resolve this, ensure that z is given a value regardless of of the contents of someList:

public int myMethod(int x, out int y, out int z)
{
    z = 0; // or whatever default value you like

    ...
}

However, you should probably consider refactoring this code. It's likely there's a better way to accomplish this. If you'd really like to return 3 different int values, you might consider using a Tuple<int, int, int> or creating a custom data type to represent the value.

Answer 2

Reason : out paramaeters must be initialised before returning from the function.

You are assigning value for parameter z inside if block so compiler could not identify whether it can be initialized or not hence initialize your parameter z before if block as below:

public int myMethod(int x, out int y, out int z)
{
    int k;
    z=0;
    foreach(int i in someList)
    {

        if(anotherMethod(out k))
        {
            z = k;
        }
        else
        {
            z = 0;
        }
    }

    y = someValue;

    return anotherValue;
}

Answer 3

If someList is empty, then z will never be assigned a value, which violates it's being an out variable. Remove the out constraint, or reconfigure your function logic.