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?

Answer 1

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.