Custom Entity Databinding: Track deleted items?

[jimmarq]

Please help me with this databinding scenario:

Suppose I have a "Person" class, and that users populate Person objects in a BindingList collection through a datagridview. Users save the Person objects to the database when they click the save button.

When the user starts the app, a person datagridview is populated with Person objects in the BindingList. The user subsequenly deletes one of the rows in the table, deletes the Person object. How can I know which objects to delete in the underlying database when the user clicks the save button, since the object has been removed from the BindingList collection?

Thanks.

[nateraaaa]

You will need to use a DataValueField when you Bind the data initially. Then when the user selects an item in the drop down list and clicks the button the item selected will have a specific value. This value should be the unique identifier for a row in your database table. You can then pass this identifier to your delete proc and delete the item that has this unique value. You will then need to rebind your data so that the drop down list will not contain the deleted item. Here is the code

DataView view = new DataView[ds.Tables[0]);
ddlList.DataTextField = "columntext"; //This will be the column that holds the text to display in your drop down list
ddlList.DataValueField = "uniqueid"; //This will be the column that contains the unique identifier for every row in your database table.
ddlList.DataBind();
 
private void btnDelete_Click(object sender, System.EventArgs e)
{
  //Call the same code above after you call your Delete proc in this method. This will get the newest version of data to display in the drop down list after the delete has occurred.
}
 

After posting this code I realized that this will help you delete an item from a drop down list but you needed code to delete a row from a datagridview. My mistake.

Nathan

[jimmarq]

Your method would work for any databound control, really. Your solution is basically to update the database as soon as the control is updated. Ideally, I would have the user trigger the database update (e.g. by using a save button). Maybe I'm try to work the issue too hard.

Thanks for the response.

[Frinavale]

Your method would work for any databound control, really. Your solution is basically to update the database as soon as the control is updated. Ideally, I would have the user trigger the database update (e.g. by using a save button). Maybe I'm try to work the issue too hard.

Thanks for the response.

Well instead of updating the same instant that the user deletes the Person...you could store the ID into an array and then go through and delete all the Persons matching the IDs during the "Save" button click.