Items collection cannot be modified when the datasource property is set error

Question

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.NET4.5

I have two windows form

error show when i need to pass data from windows form2 in textbox

to windows form1 combobox

First windows Form

found combobox inside windows form1 and I show data in it in load event of form

C#

public DataTable ShowExceltwoLanguage()
{

            OleDbConnection con = new OleDbConnection(connection);


            con.Open();
            string str = "select MemberID,MemberNameAR + ' - ' + MemberNameEN as MemberName from [MemberAR$]";
            OleDbCommand com = new OleDbCommand();
            com = new OleDbCommand(str, con);
            OleDbDataAdapter oledbda = new OleDbDataAdapter();
            oledbda = new OleDbDataAdapter(com);
            DataSet ds = new DataSet();
            ds = new DataSet();
            oledbda.Fill(ds, "[MemberAR$]");
            con.Close();
            DataTable dt = new DataTable();
            dt = ds.Tables["[MemberAR$]"];
            return dt;


}

in load event of windows form1 i write as following

C#

QrClasses qrc = new QrClasses();
  DataTable dt = qrc.ShowExceltwoLanguage();
  comboBox4.DataSource = dt;
  comboBox4.DisplayMember = "MemberName";
  comboBox4.ValueMember = "MemberID";

Second windows form

here is error

Items collection cannot be modified when the DataSource property is set show

in button1 of form2 click event

C#

if (!string.IsNullOrWhiteSpace(textBox1.Text))
                {

                       
                        var cb = ((Form1)Owner).comboBox4;
                        var index = cb.FindString(textBox1.Text);
                        if (index == -1)
                        {
                            cb.Items.Add(textBox1.Text);// in this line Additional information: Items collection cannot be modified when the DataSource property is set.
                            index = cb.FindString(textBox1.Text);
                            if (index > -1)
                            {
                                cb.SelectedIndex = index;
                                Close();
                            }
                        }
                        else
                        {

                            cb.SelectedIndex = index;
                        }
                    }

so that how to solve that if possible ?

What I have tried:

Items collection cannot be modified when the DataSource property is set Error

Posted 6-Feb-17 3:59am

ahmed_sa

Updated 6-Feb-17 8:15am

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Comments

[no name] 6-Feb-17 10:03am

It really helps things along when you actually read the error message and logically apply the error to the line of code where the error occurs.

ahmed_sa 6-Feb-17 10:40am

I get error when trying Items collection cannot be modified when the datasource property is set error if possible can any one help me

ZurdoDev 6-Feb-17 11:03am

Yes, the error explains what is happening. The control is bound to a datasource and you are trying to change the items directly. It is telling you that you cannot do that.

[no name] 6-Feb-17 11:08am

"can any one help me", apparently not judging from all of the accepted answers you have in your "questions"...
So, what is the problem here? Do you not understand the error message? It is perfectly clear. As someone that claims to be from the U.S. you should have no problem at all accessing google and finding out what the error message means. You have a combobox where the datasource property is set and you are trying to modify the collection. Either unset the data source before you modify the collection or modify the collection before you set the datasource. Just like the error message says

Karthik_Mahalingam 6-Feb-17 10:51am

are you looping the collection ?

1 solution

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OriginalGriff · Answer 1 · 2017-02-06T08:15:00

As has been said, the problem is exactly what the error message says:

Items collection cannot be modified when the DataSource property is set

Your ComboBox is DataBound - it is bound to a collection of objects from which it gets it's values. When you try to add an item to the control, you are trying to give it two different data sources - the original collection, and a new set of items - and it just doesn't want to handle that any more than you want to handle all your files being on PCs in different buildings with no network connection!

Instead of adding items to the ComboBox, add them to the underlying collection from which you told it to get the values: the DataSource.