Moving values between two listboxes

Question

0.00/5 (No votes)

See more:

I m selecting items from one listbox and adding them to second listbox on button click.the problem is tht when i want to deselect the selected items from listbox2, it gives "Object reference not set to an instance of an object" error.Below is the code I added behind SELECT button.I have used the same code for deselting with listbox1 replaced by listbox2 and vice versa.

NOTE: items in listbbox1 are being retrieved from database. and itmes tht got selected in listbox2 will be saved to databse

C#

List<int> rowIndexes = new List<int>();

foreach (int index in listBox1.SelectedIndices)
{
    DataRowView view = listBox1.Items[index] as DataRowView;

    string id = view["Course_Id"].ToString();

    string name = view["Course_Name"].ToString();

    listBox2.Items.Add(name);

    rowIndexes.Add(index);

}

try
{
    for (int i = rowIndexes.Count; i > 0; i--)
    {
       dt.Rows.RemoveAt(rowIndexes[i - 1]);

       dt.AcceptChanges();
    }

}
catch (Exception er)
{
     MessageBox.Show(er.Message);
}

Any help would be appreciated.

Posted 26-Oct-11 21:26pm

ariez88

Updated 27-Oct-11 8:19am

N_tro_P

v5

Add a Solution

Comments

phil.o 27-Oct-11 5:10am

This is only a small code snippet without any context information.
Please include the method in which it is placed, as well as the code from where you are calling this method.

3 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

**Orcun Iyigun** · Answer 1 · 2011-10-26T21:37:00

Solution 1

Do you know the magic tool called "Debugger" :) use it and will be amaze by the results.. use the Debugger in your button click code and see where the value that you are assigning is null. that's why it is throwing that error.

Posted 26-Oct-11 21:37pm

Orcun Iyigun

Abhinav S · Answer 2 · 2011-10-26T21:51:00

Solution 3

XML

List<int> row Indexes = new List<int>();

This line wont even compile.
So make sure you have copy pasted the right code here. This will help someone assist you better.

Posted 26-Oct-11 21:51pm

Abhinav S

Comments

ariez88 27-Oct-11 3:53am

its rowIndexes i dont know why its giving space between this.and it does compile easily but gives error at runtime

SercanOzdemir · Answer 3 · 2011-10-27T03:45:00

C#

foreach (int index in listBox1.SelectedIndices)
{
DataRowView view = listBox1.Items[index] as DataRowView;

string id = view["Course_Id"].ToString();

string name = view["Course_Name"].ToString();

listBox2.Items.Add(name);

rowIndexes.Add(index);

}

You have an issue there.Your assignment on rowindexes variable should return null.So when you try to reach it you 've got an exception.Check your index value with a MessageBox.Show(index); Method first.