C# - 将扩展的参数数组传递给另一个 function

Question

How can I expand a params array when passing it on to another function.

Consider the following example:

public class TestClass
{
    public static void Main()
    {
        TestParamFunc(1, "1", 1.0f, 1.0);

        Console.ReadKey();
    }

    private static void TestParamFunc(params object[] parameters)
    {
        //At the moment the DeeperTestParamFunc receives the following parameters: { int, object[] }
        //How to expand this to { int, int, string, float, double } ?
        //So that { 1, 1, "1", 1.0f, 1.0 } is received.
        DeeperTestParamFunc(1, parameters);
    }

    public static void DeeperTestParamFunc(params object[] parameters)
    {
        foreach(object obj in parameters)
        {
            Console.WriteLine(obj.GetType().ToString());
        }
    }
}

Output:

System.Int32
System.Object[]

The output that I would like to have:

System.Int32
System.Int32
System.String
System.Single
System.Double

Answer 1

You make a new array, copy the existing parameters into it, add more things and call the other method with the larger array

These are, when all is said and done, just arrays. params just means the compiler lets you specify arguments individually and it will turn it into an array for you

You write this:

MyFuncWithParamsObjectArg(1,2,3,4,5);

The compiler conceptually changes it to:

MyFuncWithParamsObjectArg(new object [] {1,2,3,4,5} );

Here's a demo program:

public static void Main()
{
    A("z", "y");
    
}

static void A(params object[] a){
    Console.WriteLine("In A()");
    
    foreach(object o in a)
        Console.WriteLine(o);
    
    object[] oo = new object[a.Length + 2];
    
    for(int i = 0; i < a.Length; i++)
        oo[i] = a[i];
    
    oo[a.Length] = "new";
    oo[a.Length + 1] = "new2";
    
    B(oo);
}

static void B(params object[] b){
    Console.WriteLine("In B()");
    
    foreach(object o in b)
        Console.WriteLine(o);
}

Prints out this:

In A()
z
y
In B()
z
y
new
new2

You can see that B was called with an array 2 longer than a, and added two more elements

Note, you can't "expand" an array, regardless of whether it's params or not. You have to make a new array, copy the stuff over, and go from there

If you're looking to wrap it up so that you're not flattening the first array, but instead making another params array that has the first array as one of its elements:

static void A(params object[] a){
    Console.WriteLine("In A()");
    
    foreach(object o in a)
        Console.WriteLine(o);
    
    B(a, "new1", "new2");
}

B will now get an array that looks like:

object[] {
   object[] { "z", "y" },
   "new1",
   "new2"
}

As noted; there is no magic - the compiler looks at what you provided and if the arguments match "called with a single dimension array" then it calls the function with the array, otherwise it scoops up the various arguments, turns them into an array, and calls it with that array

B(a);                                  //a is already an object array, it is passed in verbatim
B(a, "new1", "new2");                  //a new object array is created from these 3 objects
B(new object[] {a, "new1", "new2"} );  //manually doing what the compiler does for you above

Answer 2

this is what you want:

    private static void TestParamFunc(params object[] parameters)
    {
        // manually create the array in the form you need
        var deeperParameters = new object[parameters.Length + 1];
        deeperParameters[0] = 1;
        parameters.CopyTo(deeperParameters, 1);            
        DeeperTestParamFunc(deeperParameters);
    }

Answer 3

try:

public static void DeeperTestParamFunc(params object[] parameters)
        {
            foreach (object obj in (IEnumerable) parameters[1])
            {
                Console.WriteLine(obj.GetType().ToString());
            }
        }

instance:

public static void DeeperTestParamFunc(params object[] parameters)
    {
        foreach(object obj in parameters)
        {
            Console.WriteLine(obj.GetType().ToString());
        }
    }