Create data table in ASP.NET - Basic

Add a GridView control, two lable controls, three textbox controls and button control in the page

Create datatable structure.

private DataTable CreateDataTable()
{
DataTable myDataTable = new DataTable();

DataColumn myDataColumn;

myDataColumn = new DataColumn();
myDataColumn.DataType = Type.GetType("System.String");
myDataColumn.ColumnName = "id";
myDataTable.Columns.Add(myDataColumn);

myDataColumn = new DataColumn();
myDataColumn.DataType = Type.GetType("System.String");
myDataColumn.ColumnName = "username";
myDataTable.Columns.Add(myDataColumn);

myDataColumn = new DataColumn();
myDataColumn.DataType = Type.GetType("System.String");
myDataColumn.ColumnName = "firstname";
myDataTable.Columns.Add(myDataColumn);

myDataColumn = new DataColumn();
myDataColumn.DataType = Type.GetType("System.String");
myDataColumn.ColumnName = "lastname";
myDataTable.Columns.Add(myDataColumn);

return myDataTable;
}

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Insert data into datatable.
private void AddDataToTable(string username,string firstname,string lastname,DataTable myTable)
{
DataRow row;

row = myTable.NewRow();

row["id"] = Guid.NewGuid().ToString();
row["username"] = username;
row["firstname"] = firstname;
row["lastname"] = lastname;

myTable.Rows.Add(row);

protected void btnAdd_Click(object sender, EventArgs e)
{
if (txtUserName.Text.Trim() == "")
{
this.lblTips.Text = "You must fill a username.";
return;
}
else
{
AddDataToTable(this.txtUserName.Text.Trim(), this.txtFirstName.Text.Trim(), this.txtLastName.Text.Trim(), (DataTable)Session["myDatatable"]);

this.GridView1.DataSource = ((DataTable)Session["myDatatable"]).DefaultView;
this.GridView1.DataBind();

this.txtFirstName.Text = "";
this.txtLastName.Text = "";
this.txtUserName.Text = "";
this.lblTips.Text = "";
}
}

Be noted "Session["myDatatable"] = myDt;" is important to ensure we can add new data continually until the page be closed.
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
myDt = new DataTable();
myDt = CreateDataTable();
Session["myDatatable"] = myDt;

this.GridView1.DataSource = ((DataTable)Session["myDatatable"]).DefaultView;
this.GridView1.DataBind();
}
}