Retaining data when adding new Datatable Row

I created a dataset with a datatable.  I have a textbox and on click event of a button I add the text of the textbox as a new row to the datatable.  However everytime I add a new row, the datatable seems to lose the previous entered data. 
Why is this happening and is there a way to keep adding data to the datatable without losing the previously entered data? 
Dim myDS As DataSet = New DataSet("myDS") Dim myDT As DataTable = myDS.Tables.Add("MyTable") Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load myDT.Columns.Add("TestColumn", Type.GetType("System.String")) GridView1.DataSource = myDT End Sub Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click Dim dr As DataRow dr = myDT.NewRow() dr(&q ...