LINQPad still cannot find extension method 'Where' after adding System.Data.DataSetExtensions.dll

I have to join results from 2 sprocs in LINQ but got the error message: 'System.Data.DataSet' does not contain a definition for 'Where' and no extension method 'Where' accepting a first argument of type 'System.Data.DataSet' could be found (press F4 to add a using directive or assembly reference)

However after added the DataSetExtensions the error still appears.

Code:

var c = GetAllGameCategories (123);
var d = GetGameCategories(224开发者_运维百科58);

Var e = c.Where(....);  // Error on this line!

Any help appreciated.

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A DataSet is a collection of DataTable objects.
It does not directly contain any data.

You need to call .Where() on the DataTable.
EDIT: If it isn't a typed DataTable, you'll need to call .AsEnumerable() first.