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WinForms Application TextBox.Text = LARGE_TEXT causes the UI to update slowly. How can I improve performance?

Posted on 2009-07-06
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Last Modified: 2012-08-13
When the application tries to read a 5MB text file and assign the value to a TextBox control, it takes 3-4 seconds for the UI to update. Is there a way to improve performance?
Output.Text = TEXT_FROM_LARGE_FILE

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Question by:proaceteam
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8 Comments
 
LVL 6

Expert Comment

by:ahmad2121
ID: 24790003
You could use a loop and use substring to gradually build the string.

I would profile the situation. Basically, figure out how many characters you can put lag free (let's say its 1000), then inside your for loop, increment that substring and append it to Output.Text.

Don't forget to:

Application.DoEvents()

in your loop to allow other things to happen while it updates! You have have to introduce a few ms delay in the loop as well.
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LVL 6

Expert Comment

by:ahmad2121
ID: 24790036
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Author Comment

by:proaceteam
ID: 24790049
Some additional code to give you an idea of what is going on right now.


Dim srReadLog As New StreamReader(strOutputPath + "\" + Path.GetFileName(strOutputFileName))
Dim sb As New StringBuilder()
sb.Append(srReadLog.ReadToEnd())
OutputText.Visible = True
OutputText.Text = sb.ToString()
srReadLog.Close()

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Expert Comment

by:JackOfPH
ID: 24790596
Try putting the retrieve text directly to the textbox and not through stringbuilder.
Dim srReadLog As New StreamReader(strOutputPath + "\" + Path.GetFileName(strOutputFileName))
OutputText.Visible = True
OutputText.Text = srReadLog.ReadToEnd()
srReadLog.Close()

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Expert Comment

by:ahmad2121
ID: 24790834
Which I imagine is the exact same thing...
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LVL 15

Expert Comment

by:JackOfPH
ID: 24790950
@ahmad2121

>>Which I imagine is the exact same thing...

Nope...

If you can see... you put the contents of the file in the stringbuilder which would took approximately some seconds to do then you put that again in the textbox which will take some second again to do...

StringBuilder here is no help at all, since you where not appending or concatenate strings.

By directly putting the contents of the textfile to the textbox you remove the fraction of seconds in filling up the values in the stringbuilder.

:)

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Accepted Solution

by:
ahmad2121 earned 2000 total points
ID: 24796808
It is not even a fraction of a second. And if the compiler could optimize it away, then the argument is invalid.

Here is a better solution than the one I initially mentioned.

Here I use a bit of trickery. I know that all the parameters being passed to new string will get evaluated before the new string is created, meaning that temp will get populated.

Change count to whatever is more convenient. The bigger the count, the smaller the load time the more "laggy" it is. The smaller the count, the more snappier it is but it will take a bit longer.
        Dim srReadLog As New StreamReader(strOutputPath + "\" + Path.GetFileName(strOutputFileName))
        OutputText.Visible = True
        Dim count As Integer
        count = 40000
        Dim temp(count) As Char
        Do While srReadLog.Peek() >= 0
            OutputText.AppendText(New String(temp, 0, srReadLog.Read(temp, 0, temp.Length)))
            Application.DoEvents()
        Loop
        srReadLog.Close()

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Author Closing Comment

by:proaceteam
ID: 31600402
Thanks a lot Ahmad. That worked beautifully!
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