DataSet from Method returns error

[leviwatts]

Exception Details: System.Argument Exception: DataTable already belongs to another DataSet.
Googling for this error shows several post of people trying to manipulate a table within a dataset. Others suggest using .clone() and .copy(). Neither results in a different error.

Within another class, I've gathered two tables of data for a nested repeater. To return a table, int, string or anything else in C#, one sets their local variable equal to the returned data of the method. Doing this with a DataSet provides the above error.

Q: How do I pull a DataSet returned from a method equal to a local DataSet variable?

It is a web site, though I believe this to be a C# syntax issue. Let me know if I'm wrong.

OS: Windows XP SP3
MS VS 05 v8.0.50727.42
.NET 2.0.50727

//Within main class
int[] iaInvID = {2,5,8,11};
DataSet ds = new DataSet();
ds = MyDll.MyDllsClass.ReturnSalesSummary(iaInvID);

//Within MyDll.MyDllsClass class
public static DataSet ReturnSalesSummary(int[] iaInvID)
{
    DataSet ds = new DataSet();

    ds = CreateRelationshipTable(ds, iaInvID);
    ds.Tables.Add(ReturnSalesSummary_DummySet(iaInvID));

    ds.Relations.Add("InvID",
	ds.Tables[0].Columns["InvID"],
	ds.Tables[1].Columns["InvID"]);

    return ds;
}

private static DataSet CreateRelationshipTable(DataSet ds, int[] iaInvID)
{
    //For each id, create a row of that id.  This allows a one to many relationship
    //with the table from the db.
    DataTable dt = ds.Tables.Add("InvIDs");
    dt.Columns.Add("ID", typeof(int));
    foreach (int i in iaInvID)
	dt.Rows.Add(i);
    return ds;
}

private static DataTable ReturnSalesSummary_DummySet(int[] iaInvID)
{
    //Until the SQL statement is correct, create a dummy table of similar data.
    DataSet ds = new DataSet();
    DataTable dt = ds.Tables.Add();

    dt.Columns.Add("RowID", typeof(int));
    dt.Columns.Add("InvID", typeof(int));
    dt.Columns.Add("StationID", typeof(string));

    int iCount = 0;
    string[] saStationID = { "Workstation 1", "Workstation 2", "Online Sales" };

    foreach (int i in iaInvID)
	for( int i2 = 0; i2 < 3; i2++)
	{
	    dt.Rows.Add(iCount, i, saStationID[i2]);
	    iCount++;
	}

    return ds.Tables[0];
}

[Plater]

I think you need to use the .Copy() method to make a copy of the DataTable object if you want to insert it into another dataset. (Just like you would with DataRows)

[leviwatts]

I think you need to use the .Copy() method to make a copy of the DataTable object if you want to insert it into another dataset. (Just like you would with DataRows)

//Within main class
ds = Pyramedium_Enterprise_Reporting.Report_TenderSummaries.ReturnSalesSummary(iaInvID).Copy();

As before, this results in the same error. Am I using .Copy() wrong?

[leviwatts]

[Edit limit expired]
The error pointed out the method at line 4 of the first set of code, making me assume that was the line causing the issue. Using .Copy() in line 7 of the second set of code pushes me to a new error message.

ds.Tables.Add(ReturnSalesSummary_DummySet(iaInvID).Copy());

Thanks Plater.