Hi,
assuming you're asking for a WinForms solution and your "listbox1" is a standard ListBox control, your problem is - apart from the last line, which prevents your code from getting compiled - the wrong DataSource.
A DataSet is a set of Tables, Rows, Relations ... so it is of no use as a DataSource. If you want to display a specific column from a specific table from your DataSet, you must specify this. So use
this.listBox1.DataSource = sds.Tables["TblCategories"];
this.listBox1.DisplayMember = "Description";
instead of
listBox1.DataSource = sds;
And maybe you should consider using "using"-blocks to secure the disposal of the SqlConnection, the SqlCommand and the SqlAdapter.
Cheers
Jürgen