Get typeof DataGrid data and cast as it

Question

I'm having a problem with getting data of gridview and convering it into DataTable. Acually its like some of datagrids in my application have ItemsSource which I can cast as DataView, but another got ItemsSource defined in application.

For example:

DataGrid1 - ItemsSource = DataView (straight from database) DataGrid2 - ItemsSource = ObservableCollection of Product DataGrid3 - ItemsSource = ObservaleCollection of Categories

Error I'm getting:

Unable to cast object of type System.Collections.ObjectModel.ObservableCollection`1[myApp.Product] to type System.Data.DataView.

I want to reach something like this:

  DataTable dt = null;
  try
  {
       dt = ((DataView)dg.ItemsSource).ToTable();
  }
  catch
  {
       Type t = dg.ItemsSource.GetType();
       dt = ((t)dg.ItemsSource).ToTable();
  }

So actually I'd like to get collection as object and cast ItemsSource as DataTable.

Is it even possible?

Answer 1

Yes, it is possible... your error said

Unable to cast object of type 'System.Collections.ObjectModel.ObservableCollection`1[myApp.Product]' to type 'System.Data.DataView'

This means that there is no direct casting relationship between these classes. In order to provide that, you'd have to extend the ObservableCollection<T> class and override the explicit cast operator:

public class MyObservableCollection : ObservableCollection<YourDataType>
{
    public static explicit operator DataView(MyObservableCollection collection)
    {
        DataTable table = new DataTable();
        foreach (YourDataType item in collection)
        {
            // fill your DataTable however you want to here
        }
        return new DataView(table);
    }
 }

You can find out more from the explicit (C# Reference) page at MSDN. You can find out how to fill a DataTable from the DataView.Table Property page at MSDN.

UPDATE >>>

This is not a method. It is a cast operator. It is used for casting one type into another. Like (int) in the following example:

int intValue = (int)doubleValue;

You asked how to cast an ObservableCollection into a DataView. My answer shows you how to do exactly that:

DataView dataView = (DataView)yourCustomObservableCollection;

Or from YOUR example:

dt = ((DataView)dg.ItemsSource).ToTable();

... assuming that there is an instance of this custom MyObservableCollection set as the dg.ItemsSource.

You said

DataGrid2 - ItemsSource = ObservableCollection of Product DataGrid3 - ItemsSource = ObservaleCollection of Categories

1. So first, create a new class like I showed you... call it whatever you like.

2. Next, replace your current ObservableCollection instances with your new MyObservableCollection instances.

That's it. I don't know how to explain it any more than that. If you really don't understand this, then you have no place asking these questions. I suggest that you go to MSDN to learn all about casting and then come back to make sense of this.