Parameter count mismatch with Invoke?

Question

The code block below results in the error: TargetParameterCountException was unhandled by user code. Parameter count mismatch.

    public void AddListViewItem(string[] Data)
    {
        if (InvokeRequired)
        {
            Invoke(new Action<string[]>(AddListViewItem), Data);
        }
        else
        {
            ListViewData.Items.Add(Data[0]).SubItems.AddRange
            (
                new string[]
                { 
                    Data[1],
                    Data[2],
                    Data[3],
                }
            );
        }
    }

Any ideas?

What's the signature of `AddListViewItem`? – Daniel Renshaw Sep 15 '10 at 21:09 — Daniel Renshaw, Sep 15 '10 at 21:09
It's right there. He's calling it recursively. – BFree Sep 15 '10 at 21:10 — BFree, Sep 15 '10 at 21:10
Make sure to accept the answer that solved your problem. – BFree Sep 15 '10 at 21:13 — BFree, Sep 15 '10 at 21:13

Ani · Accepted Answer · 2010-09-15T21:24:47.487

26

The error occurs because of array covariance; an array of strings is assignable to object[]. This causes the Invoke method to treat each element of the string array as if it should be an argument to the AddListViewItem method.

Here's a fix:

Invoke(new Action<string[]>(AddListViewItem), new object[] {Data});

(or)

Invoke(new Action<string[]>(AddListViewItem), (object)Data);

This makes it crystal-clear to Invoke that the target method takes a single parameter.

edited Sep 15 '10 at 21:24

answered Sep 15 '10 at 21:08

Ani

111,048
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@Ani, Could you explain what is array covariance? better with an example. Thanks. – smwikipedia Apr 18 '13 at 16:00
Thanks! This was driving me crazy. Your first example worked well in my situation. I was passing an object array, but the invoke method isn't smart enough to handle it as-is. Example... `.Invoke(mysource, new object[] {myobjectarray});` – John Suit Jul 02 '15 at 15:51

score 0 · Answer 2 · edited Apr 15 '14 at 12:09

0

UPDATE information:

If you are using Windows Server 2008 R2, take a look at Windows Update for .Net Framework 4.5.1 for Windows Server 2008 R2 x64 based systems KB2858725. For me, after installed this update fixed this issue.

edited Apr 15 '14 at 12:09

Rahil Wazir

10,007
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answered Apr 15 '14 at 11:46

Willian

1

Parameter count mismatch with Invoke?

2 Answers2

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