Question

I have a static class with method:

public static class FooUtilities
{
   public static FooStruct[] GetFooBar(int foo)
   {
      var fooStruct = new FooStruct[];
      // Connect to SOAP API, collect data to put in fooStruct
      ...
      return fooStruct;
   }
}

Now I want to use the result of GetFooBar(int foo) as an argument to another method that uses the results of this method to create new fooItem items, something like:

public static FooItem CreateFooItem(fooResult = GetFooBar(int foo))
{
   var fooItem = new FooItem(fooResult[0].value, fooResult[1].value,fooResult[2].value);
   ...
   return fooItem;
}

The way I do it now is to write this:

public static FooItem CreateFooItem(FooStruct[] fooResult)
{
   var fooItem = new FooItem(fooResult[0].value, fooResult[1].value,fooResult[2].value);
   ...
   return fooItem;
}

This works, but then I have to call the method like:

FooItem myItem = FooUtilities.CreateFooItem(FooUtilities.GetFooBar(12321));

What I’d like is to be able to call:

FooItem myItem = FooUtilities.CreateFooItem();

And have the argument included implicitly when this method is called.

Is this possible?

Answer 1

You can’t do this. From the spec:

A default value must be one of the following types of expressions:

• a constant expression;

• an expression of the form new ValType(), where ValType is a value type, such as an enum or a struct;

• an expression of the form default(ValType), where ValType is a value type.

If you’d tried your CreateFooItem(fooResult = GetFooBar(int foo)) example, you’d have got the compiler error "Default parameter value for ‘fooResult’ must be a compile-time constant" which is a shorter version of the above.