if have an Arraylist filled with structs and the struct is:

public struct myTables
{
   Type DsType; // Contains the System.Type of the strongly typed dataset
   DataSet Data; // Contains the dataset
}

// the code that fills the list
this.List.Add( new MyTables(typeof(MyTable1), MyTable1) );

Now i want to get a dataset from this arraylist and cast it to it's base type, how would i do that.