CODEWITHSUNDEEP
c#scrollbar
user6262035
user6262035

Reputation:

Scroll Bar click event method running twice c#

I have a user control that uses a vertical scroll bar to browse through it. Each time I click on a min button of the scroll bar it executes the called method properly but instead of exiting, following the return from the called method, it recalls the method a second time. Basically the scroll bar event is firing twice updating its value each time. Why?

Here is a condensed version of my code....

private void vScrollBar1_Scroll(object sender, ScrollEventArgs e)
    {
       ThreadTest((ushort)vScrollBar1.Value);
    }

    private void ThreadTest(ushort value)
    {
        if (mC6800Screen1.InvokeRequired)
        {
            TestCallBack tcb = new TestCallBack(displayVirtualMemory);
            Invoke(tcb, new object[] {value});
        }
        else
        { 
            displayVirtualMemory(value);
        }
    }

    private void displayVirtualMemory(ushort value)
    {
        //This method simply displays the contents of an array [0 - 0xffff]
        //16 rows at a time.  
        for (ushort row = value; row < value + 400; row += 16)
        {
            //Compute the index offset (16 bits per row)
            string indexOffset = row.ToString("X4");
            var indexChars = indexOffset.ToCharArray();
            //Display memory index
            for (ushort arrayPosition = 0; arrayPosition < indexOffset.Length; arrayPosition++)
            {
                mC6800Screen1.screenMemory[screenPosition] = (byte)indexChars[arrayPosition];
                screenPosition += 2;
            }

            screenPosition += 4;
        }       
        //the data is copyied to a bitmap which is transfered to a user control
        //once all the processing is complete.
        mC6800Screen1.Invalidate();
        mC6800Screen1.Update();
    }

Upvotes: 0

Views: 856

Answers (1)

user6262035
user6262035

Reputation:

After much web browsing, I discovered that an EndScroll event is being created following the initial SmallIncrement event. Why this occurs is beyond my grey matter! I changed the vScrollbar event handler as follows:

private void vScrollBar1_Scroll(object sender, ScrollEventArgs e)
    {
        if (e.Type == ScrollEventType.EndScroll) return;
        ThreadTest((ushort)vScrollBar1.Value);
    }

Upvotes: 3

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