VS 2010 - How To Do A Query From A Dataset

Can you do a query from a dataset?

Code:

Dim cmd As New SqlCommand
cmd.Connection = New SqlConnection(<connectionString here>)
cmd.Connection.Open()
cmd.CommandText = "Select * From table_name"
Dim da As New SqlDataAdapter(cmd.CommandText, cmd.Connection)
Dim ds As New DataSet
da.Fill(ds) ' I want to do some query with THIS dataset
cmd.Connection.Close()

I want to do a query based on the dataset ds. Let's say I want to filter out names that starts with "a". If yes, how do you do it?