Object reference not set to an instance of an object.

Question

1.00/5 (1 vote)

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I have a WPF Media Player. While I try to display the percentage of Volume in the Label. I have written the following codes in sliderVolume.ValueChanged event.

C#

private void sliderVolume_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
        {
            isMuted = false;
            mePlayerMain.IsMuted = false;
            mePlayerMain.Volume = sliderVolume.Value;
            double per = ((sliderVolume.Value / sliderVolume.Maximum) * 100);
            String value = per.ToString();
            //Console.WriteLine(per.ToString());

            if (!(String.IsNullOrEmpty(value)))
                lbVolumePercent.Content = value;
            else
                lbVolumePercent.Content = "";
        }

Every time I try to run the project it throws an exception in BOLD line saying that Object Reference is not set to instance of an object.

Can you help me out? Thanks.

Posted 1-Nov-11 5:23am

Jyoti Choudhury

Updated 1-Nov-11 5:35am

André Kraak

v3

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Comments

Sergey Alexandrovich Kryukov 1-Nov-11 12:35pm

Not all relevant code is shown, as Griff explained.
--SA

2 solutions

Solution 2

The best thing to do is to debug and step through code. Where-ever you get an error, you can stop at that point, take a look at that code and then figure out where the null is.

Posted 1-Nov-11 5:50am

Abhinav S

Comments

Sergey Alexandrovich Kryukov 1-Nov-11 12:34pm

Exactly. Voted 5.
--SA

Abhinav S 1-Nov-11 12:35pm

Thank you SA.

Jyoti Choudhury 7-Nov-11 13:03pm

thanks...

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OriginalGriff · Accepted Answer · 2011-11-01T05:34:00

Solution 1

Since you don't show us where you set (or even declare) the lbVolumePercent variable, we can only assume that you aren't setting it anywhere - it is the only part of that line which would normally throw that exception.

Put a breakpoint on the line, and see when it is occurring - it may be that it occurs before you actually get round to setting the variable it is referring to.

Posted 1-Nov-11 5:34am

OriginalGriff

Comments

Jyoti Choudhury 1-Nov-11 11:44am

lbVolumePercent is not a variable. It's a user control Label.

OriginalGriff 1-Nov-11 11:48am

That still makes it a variable. And if it isn't null, and it's your user control, then you need to single step into the control to identify why setting the property is causing the problem.

Sergey Alexandrovich Kryukov 1-Nov-11 12:34pm

Sure, a 5.
--SA

Jyoti Choudhury 7-Nov-11 13:04pm

thanks Griff and SA