Question

Why would this happen?

You start up a thread, and it runs a class.

Inside that class there is a for loop, inside the for loop there is a “write to messagebox” and another class.

Why does the order in witch I put the write and the class (which one happens first) effect the accuracy of my data?

(This is inside the class that the thread is running)

int atPDFNumber= 0
foreach (var z in q)
        {
                atPDFNumber++;

                convertToImage(z.FullName);

                txtboxtest.BeginInvoke(
            ((Action)(() => txtboxtest.Text += atPDFNumber.ToString())));
}

That output gives me some overlapping values. the output is

Run 1 : 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Run 2 : 1 3 3 4 5 6 7 8 9 10 11 12 13 14

Run 2 : 1 2 3 4 5 6 7 8 9 11 11 12 13 14

Where this Runs them all in the correct order

foreach (var z in q)
            {
                    atPDFNumber++;

                txtboxtest.BeginInvoke(
                ((Action)(() => txtboxtest.Text += atPDFNumber.ToString())));

               convertToImage(z.FullName);

Why does that happen? It might be that the external method i use in the class ConvertToImage is also running a thread.. in that case, how would i “pause” my thread to wait for the ConvertToImage to finish…

Other wise i have no idea why this thread acts the way it does?

Answer 1

Your action is capturing the value of atPDFNumber variable, not the current value of it. In your example if you assing atPDFNumber to a local variable and pass it to your action it will work as expected.

int atPDFNumber = 0; 
foreach (var z in q)
{
    atPDFNumber++; 
    convertToImage(z.FullName);
    int currentValue = atPDFNumber;
    txtboxtest.BeginInvoke(((Action)(() => txtboxtest.Text += currentValue.ToString())));
}

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Here you can find about Variable Capturing in C#