"BindingSource cannot be its own data source" - error when trying to reset the binding source from a method in another class

Question

We are binding a DataGridview using BindingSource. So in the main thread we have given like this.

            class1BindingSource = new BindingSource();
            class1BindingSource.DataSource = class1List;  
            this.dataGridView1.DataSource = class1BindingSource;

After that i have a placed a background worker in the form and is triggering in a button click.

i.e. in the button click

this.backgroundWorker1.RunWorkerAsync()

In the BackgroundWorker DoWork Event i am trying to update the BindingSource and there by trying to update the DataGridview.

So the BindingSource reset is done in a method in another class.

DoWork Event

Class2 cl2 = new Class2();
cl2.UpdateBindingSource(class1BindingSource);

UpdateBindingSource Method

public void UpdateBindingSource(BindingSource bs)
        {
            Class1 c1 = bs.Current as Class1;    
            for (int i = 0; i < 1000; i++)
            {
                lock (bs.SyncRoot)
                {
                    c1.MyProperty1 = i;
                    bs.ResetItem(0);
                }
            }
        }

Now i am getting an exception like BindingSource cannot be its own data source. Do not set the DataSource and DataMember properties to values that refer back to BindingSource.

If i am doing this in my DoWork Event then i can reset the item in the control thread itself using BeginInvoke method.

But actually i am trying to simulate our application scenario. So i want to solve this in this format.

Can any one help me on this.

Answer 1

The problem is that you can't update a BindingSource within a thread other than the gui thread. This is due the fact, that the BindingSource will fire some events which will then be received by your data grid view which will then start to update itself, which will fail cause it won't be done on the gui thread.

So right before you call RunWorkerAsync() you should call class1BindingSource.SuspendBinding() and within your RunWorkerCompleted you should call class1BindingSource.ResumeBinding().

Also ensure that within your DoWork you won't call any methods on the binding source (like you did with bs.ResetItem(0)).

And also remove this lock statement. It simply doesn't make any sense (in your example) and if you really need it (in your real code) consider using some private object _Gate = new Object(); within your class to avoid any deadlocks from the outer world, cause bs.SyncRoot is publicly available.