Problem with optional argument

[ed57gmc]

Here is the signature of my method.

        public static void Redefine(this BlockReference blkRef, Transaction trans, string path, Blocks.RedefineAction flag, string blockname = "")
        {
            string text = "";
            if (blockname == "")
            {
                text = blkRef.Name;
            }

If I call it without specifying the last optional argument, I get an invalid input error. If I call it with a string, it works, but if I call it with and empty string "" to get around the first error condition, I still get an invalid argument error. What am I missing? Thanks in advance.

[kdub_nz]

I'd need to see your input Ed

This works for me ac2023 vs2022 4.8

    public class Commands
    {
        private static Document _doc = AcadApp.DocumentManager.MdiActiveDocument;
        private static Database _db = _doc.Database;
        private static Editor _ed = _doc.Editor;

        [CommandMethod("TEST")]
        public static void Test()
        {
            _ed.WriteMessage("Redefine Test\n");

            Redefine("");
            Redefine("", "oranges");
        }

        public static void Redefine(
                            string path,
                            string blockname = "")
        {
            string textValue = "something";
            //if (string.IsNullOrEmpty(blockname))
            if (blockname == "")
            {
                textValue = "nothing";
            }
            _ed.WriteMessage($"{textValue}\n");
        }
    }

I thought initially the issue may have been with the equality conditional, but it seems OK

Regards,

[ed57gmc]

Well here are the scenarios:

// returns error
oldBlk.Redefine(trans, sTitleBlock, Blocks.RedefineAction.PreserveAttValues);

// returns erro
oldBlk.Redefine(trans, sTitleBlock, Blocks.RedefineAction.PreserveAttValues, "");

// No error
oldBlk.Redefine(trans, sTitleBlock, Blocks.RedefineAction.PreserveAttValues, "test");

[kdub_nz]

Ed, 

Would you happen to also have an overloaded version of that Method ??

[kdub_nz]

FWIW :

[ed57gmc]

No, I only have just the one method definition. I thought about using named parameters, but I thought it should work without it.

[ed57gmc]

I tried the following and it still caused an error. Scratching my head. 😟

oldBlk.Redefine(trans: trans, path: sTitleBlock, flag: Blocks.RedefineAction.PreserveAttValues, blockname: "");

[ed57gmc]

Below is what the signature looks like in the utility dll, but when I compile it, the referenced dll looks like the first post.

        public static void Redefine(this BlockReference blkRef,
                                    Transaction trans,
                                    string path,
                                    Blocks.RedefineAction flag,
                                    [Optional] [DefaultParameterValue("")] string blockname)
        {

            // store correct name
            string newName = "";
            if (blockname == "")
            {
                //use filename as blockname
                //assume path is .dwg
                newName =  Path.GetFileName(path);
                newName = newName.Remove(newName.Length - 4);
            }

 I modified this definition to get rid of the attribute tags and just assign a default value with (string blockname = ""), but this too still fails with invalid input error. The only thing I can see that I'm doing different from you is that this extension method is defined in a utility dll that is referenced into the solution.

[norman.yuan]

with "string" type, null is not equal to "" (empty string). So, if you call the method with a string argument as optional and not passing anything, then that argument is null, not "". Now you can see why "if (blockname == "")' would raise error, because variable blockname is null: you cannot compare null to anything other than null.

The correct code should be

if (!string.IsNullOrEmpty(blockname)

{

    ...

}

[ed57gmc]

Ok, I changed the logic of the if statement, but during debug, I can't even step into the redefine method. I still get the invalid input error. It never makes it to the logic test.

[ed57gmc]

I'm still fighting with this optional argument. I thought it might be a problem with assigning the default value to an empty string, so I changed the default to null, but this errors too.

//calling sub
oldBlk.Redefine(trans: trans, path: sTitleBlock, flag: Blocks.RedefineAction.PreserveAttValues);

//method signature
       public static void Redefine(this BlockReference blkRef, Transaction trans, string path, Blocks.RedefineAction flag, string blockname = null)
        {
            string text = "";
            if (string.IsNullOrEmpty(blockname))
            {
                text = Path.GetFileName(path);
                text = text.Remove(text.Length - 4);
            }

[_gile]

Hi,

You should give more informations because there's nothing wrong in the extract of code you show.

What's the error?

Which expression causes this error?

Here's a little testing example which focus on the optional string argument:

        [CommandMethod("CMD1")]
        public static void Cmd1()
        {
            OptionnalArgumentTest(@"B:\Desktop\Example.dwg");
        }

        [CommandMethod("CMD2")]
        public static void Cmd2()
        {
            OptionnalArgumentTest(@"B:\Desktop\Example.dwg", "SomeBlockName");
        }

        static void OptionnalArgumentTest(string path, string blockName = null)
        {
            string text = string.IsNullOrEmpty(blockName) ?
                Path.GetFileNameWithoutExtension(path) :
                blockName;
            Application.ShowAlertDialog(text);
        }

[ed57gmc · Accepted solution]

It was a stupid simple omission. I left out the 'else' keyword and newName was getting reset to "". 😧

        public static void Redefine(this BlockReference blkRef,
                                    Transaction trans,
                                    string path,
                                    Blocks.RedefineAction flag,
                                    string blockname = null)
        {

            // store correct name
            string newName = "";
            if (string.IsNullOrEmpty(blockname))
            {
                //use filename as blockname
                //assume path is .dwg
                newName =  Path.GetFileNameWithoutExtension(path);
            }
            else //<<missing
            {
                newName = blockname;
            }

[kdub_nz]

Ed,
I'm stumped too. 
For me on  ac2023, vs2022, 4.8,

//
public static void OptionTest(
                    string path,
                    string blockname = null)
{
    string textValue = (string.IsNullOrEmpty(blockname)) ? "nothing" : "something";

    _ed.WriteMessage($"\n{textValue}\n");
}

//-----------
// Test statements
    _ed.WriteMessage("Optional Parameter Test\n");

    OptionTest("YellowBrickRoad");
    OptionTest("YellowBrickRoad", "oranges");
    OptionTest("YellowBrickRoad", "");
    OptionTest("YellowBrickRoad", null);

Result :

What happens if you take something like this to a console app ??

added:
ahhh, it was resolved while I was composing this . . .  must learn to type faster 🙂