Unable to cast object of type 'system.data.datatable' to type

I have a datatable AVT of type开发者_C百科 AvailDataTable. The following code works to create a new datatable from AVT:

AvailDataTable AVT1 = (AvailDataTable) AVT.DefaultView.Table;

However, the code:

AvailDataTable AVT1 = (AvailDataTable) AVT.DefaultView.ToTable();

fails with the message "Unable to cast object of type 'system.data.datatable' to type 'AvailDataTable'.

Can someone explain why the first cast works but the second one doesn't? Thanks!

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DataView.Table returns you the underlying source DataTable, in your case this source table is of type AvailDataTable.

http://msdn.microsoft.com/en-us/library/system.data.dataview.table.aspx

Whereas DefaultView.ToTable constructs a new instance of a DataTable based on the rows in the current view.

Subtle difference here but ToTable returns you a generic DataTable object not your specific DataTable type

http://msdn.microsoft.com/en-us/library/a8ycds2f.aspx