I have been doing a lot of web service work for my job lately. I am getting data back from application and returning it to PeopleSoft. I ran into a small issue when trying to setup a new DataSet. I wanted to include only certain rows of data from one of the tables that I was getting back in the DataSet that the web application, which I am integrating into our online system, was returning.
The line of code that I was using to add the DataTable to my DataSet was quite simple...
dtNewData.Tables.Add( dsAppData.Tables[0] );
Almost immediately, I found that was causing a real problem. I kept getting an error that said “DataTable already belongs to another DataSet”. I did some searching on Google and finally found that you cannot simply add a table to a DataSet that already exists in another DataSet. Luckily, there are ways around this.
The most simple way to get around this issue is to make a copy of the table before adding. This is achieved with a very simple change to the line of code above:
dtNewData.Tables.Add( dsAppData.Tables[0].Copy() );
Unfortunately, this did not meet my needs, because I only need the first few rows of data from the original table. My final code ended up looking like this:
dtNewData = dsAppData.DataSet.Copy();
while (dsAppData.Tables[0].Rows.Count > RequestedRows)
{
DataRow dr = dsAppData.Tables[0].Rows[dsAppData.Tables[0].Rows.Count-1];
dsNewData.Tables[0].Rows.Remove(dr);
}
This created a copy of the entire DataSet and just removes the unwanted rows at the end of the table. Originally, I did a clone of the table and used ImportRow(), but this method seems to be just a little faster.
