Wsrtjtyk

Here is the scenario:
I have an Edit Dialog form with a BindingSource and some data bound text boxes on it:

I pass an entity to the form constructor and it gets loaded into BindingSource.DataSource which causes the data bound controls to show the values of properties.

The problem is as the user edits the values in TextBox controls and Validating events get passed, the data source gets changed though it is not applying to DB but it still can confuses the user as he sees the edited values on the List Form, till next application restart.

so the question is: How to prevent binding source from reflecting changes instantly or how to roll them back?

I inherited the binding source and created a new binding source like this:

public class SuperBindingSource:BindingSource

{

    #region Properties



    public object DataSourceBeforeChange { get; private set; }



    #endregion



    #region Methods



    public void ResetChanges()

    {

        this.DataSource = this.DataSourceBeforeChange;

    }



    #endregion



    protected override void OnDataSourceChanged(EventArgs e)

    {

        base.OnDataSourceChanged(e);



        DataSourceBeforeChange=this.DataSource.DeepClone();

    }

}

Though I am not sure if it is a good approach.

As an option, when setting up data-bindings, you can set them to update data source never.

Then at the point that you want to apply changes, for example when pressing OK button, you can set data-bindings to update data source on property change and then call end edit method of the binding source.

For Cancel button, you don't need to do anything, because the data source is not updated.

Example

In form load event:

this.BindingContext[bindingSource].Bindings.Cast<Binding>().ToList()

    .ForEach(b=>b.DataSourceUpdateMode= DataSourceUpdateMode.Never);

When pressing OK:

this.BindingContext[productBindingSource].Bindings.Cast<Binding>().ToList()

    .ForEach(b => b.DataSourceUpdateMode = DataSourceUpdateMode.OnPropertyChanged);

productBindingSource.EndEdit();

You can download/clone the full source code:

• r-aghaei/SuspendDataBindingExample

You can use the SuspendBinding method after the values are loaded.

After that the values should not update the source until you call ResumeBinding:

SuspendBinding and ResumeBinding are two methods that allow the temporary suspension and resumption of data binding in a simple-binding scenario. You would typically suspend data binding if the user must be allowed to make several edits to data fields before validation occurs. For example, if one field must be changed in accordance with a second, but where validating the first field would cause the second field to be in error.

According to the documentation you should be able to use this with your textboxes. If the user clicks Ok to save the values you resume the binding and if he cancels you don't.