CODEWITHSUNDEEP
c#.netmultithreading
Aaron McKelvie
Aaron McKelvie

Reputation: 167

TargetParameterCountException: Parameter count mismatch on invoke - delegate

I have the following code (removed unrelated)

//top of class declaration
private delegate void UpdateFormElements(string status, bool addEmptyRow);

//inside a function in my class
if(lboImages.InvokeRequired)
{
   lboImages.Invoke((UpdateFormElements)delegate { UpdateListBox("some text", true); });
}

private void UpdateListBox(string line, bool addEmptyRow)
{
    lboImages.Items.Add(line);
    if (addEmptyRow)
    {
        lboImages.Items.Add("");
    }
}

Basically I'm trying to pass two parameters to the UpdateListBox function to test whether to add an empty line or not to my listbox, but I am getting the error in the title. I have tried putting the two values in an object[] but it doesn't seem to change anything as I still get the error.

I'm still new to using threads so not really sure where I'm going wrong here.

Upvotes: 0

Views: 1236

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1500495

It's not clear why you're trying to use an anonymous method here. The problem is that you're creating a delegate type with two parameters, but you're not passing arguments (values for those parameters) into Invoke.

I suspect you just want:

lboImages.Invoke((UpdateFormElements) UpdateListBox, "some text", true));

That uses a method group conversion to create an UpdateFormElements delegate, and provides it the two arguments it needs.

Alternatively, you could just use a lambda expression:

MethodInvoker invoker = () => UpdateListBox(line, addEmptyRow);
lboImages.Invoke(invoker);

Upvotes: 2

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