ASP.NET - Problem with GridView with Dynamic Columns - asp.net

Question

I have a GridView that includes BoundField and TemplateField elements. Some of the TemplateField elements are dynamically generated. For the sake of reference, here is the GridView that I am using
<asp:GridView ID="myGridView" runat="server" AutoGenerateColumns="False"
DataKeyNames="ID" ShowFooter="True" EnableModelValidation="True"
OnLoad="myGridView_Load" OnRowCommand="myGridView_RowCommand"
OnRowEditing="myGridView_RowEditing" OnRowDeleting="myGridView_RowDeleting"
OnRowCancelingEdit="myGridView_RowCancelingEdit"
OnRowUpdating="myGridView_RowUpdating">
<Columns>
<asp:BoundField DataField="Number" Visible="true" HeaderText="Test" />
<asp:TemplateField HeaderText="Number">
<EditItemTemplate>
<asp:TextBox ID="tb1" runat="server" Text='<%# Bind("Number") %>' />
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="lb1" runat="server" Text='<%# Bind("Number") %>' />
</ItemTemplate>
<FooterTemplate>
<asp:TextBox ID="ftb" runat="server" Text="[x]" />
</FooterTemplate>
</asp:TemplateField>
<%-- Dynamically Generated Columns Will Be Inserted Here --%>
<asp:TemplateField HeaderText="Actions">
<EditItemTemplate>
<asp:LinkButton ID="ulb" runat="server" Text="update" CommandName="Update" />
<asp:LinkButton ID="clb" runat="server" Text="cancel" CommandName="Cancel" />
</EditItemTemplate>
<FooterTemplate>
<asp:LinkButton ID="slb" runat="server" Text="insert"
OnClick="saveLinkButton_Click" />
</FooterTemplate>
<ItemTemplate>
<asp:LinkButton ID="elb" runat="server" Text="edit" CommandName="Edit" />
<asp:LinkButton ID="dlb" runat="server" Text="delete" CommandName="Delete" />
</ItemTemplate>
</asp:TemplateField
</Columns>
<EmptyDataTemplate>
<table border="0" cellpadding="0" cellspacing="0">
<tr><td>Number</td></tr>
<tr>
<td><asp:TextBox ID="ntb" runat="server" /></td>
<td><asp:LinkButton ID="slb2" runat="server" Text="save" OnClick="saveLinkButton_Click" /></td>
</tr>
</table>
</EmptyDataTemplate>
</asp:GridView>
When the GridView initially loads, everything is loaded properly. However, anytime I perform a command (edit, insert, delete), all of the data goes away. Oddly, the BoundField values still appear correctly. However, any TemplateField does not seem to get rendered. The code that I am using to work with this GridView is here:
public partial class GridView : System.Web.UI.Page
{
private List<string> dynamicColumnNames = new List<string>();
protected void Page_Load(object sender, EventArgs e)
{
LoadPageData();
}
protected void saveLinkButton_Click(object sender, EventArgs e)
{
}
protected void myGridView_Load(object sender, EventArgs e)
{
if (Page.IsPostBack == false)
{
BindGridData();
}
}
protected void myGridView_RowCommand(object sender, GridViewCommandEventArgs e)
{ }
protected void myGridView_RowEditing(object sender, GridViewEditEventArgs e)
{
myGridView.EditIndex = e.NewEditIndex;
BindGridData();
}
protected void myGridView_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
LoadPageData();
BindGridData();
}
protected void myGridView_RowCancelingEdit(object sender, EventArgs e)
{
myGridView.EditIndex = -1;
BindGridData();
}
protected void myGridView_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
myGridView.EditIndex = -1;
LoadPageData();
BindGridData();
}
private void BindGridData()
{
// Create a temporary data source
DataTable tempData = new DataTable();
tempData.Columns.Add("ID");
tempData.Columns.Add("Number");
// Dynamically add template columns
foreach (string columnName in dynamicColumnNames)
{
tempData.Columns.Add(columnName);
TemplateField templateField = new TemplateField();
templateField.HeaderTemplate = new MyTemplateField(ListItemType.Header, columnName);
templateField.ItemTemplate = new MyTemplateField(ListItemType.Item, columnName);
templateField.EditItemTemplate = new MyTemplateField(ListItemType.EditItem, columnName);
templateField.FooterTemplate = new MyTemplateField(ListItemType.Footer, columnName);
myGridView.Columns.Insert(2, templateField);
}
// Add some phony data
Random random = new Random(DateTime.Now.Millisecond);
for (int i = 0; i < 10; i++)
{
DataRow tempRow = tempData.NewRow();
tempRow["Number"] = (i + 1);
foreach (string column in dynamicColumnNames)
tempRow[column] = random.NextDouble();
tempData.Rows.Add(tempRow);
}
// Bind the data to the grid
myGridView.DataSource = tempData;
myGridView.DataBind();
}
private void LoadPageData()
{
dynamicColumnNames.Add("USA");
dynamicColumnNames.Add("Japan");
dynamicColumnNames.Add("Mexico");
}
}
internal class MyTemplateField : ITemplate
{
// The type of the list item
private ListItemType listItemType;
// The value to use during instantiation
private string value1 = string.Empty;
public MyTemplateField(ListItemType listItemType, string value1)
{
this.listItemType = listItemType;
this.value1 = value1;
}
public void InstantiateIn(Control container)
{
if (listItemType == ListItemType.Item)
{
TextBox textBox = new TextBox();
textBox.ReadOnly = true;
textBox.DataBinding += new EventHandler(textBox_DataBinding);
container.Controls.Add(textBox);
}
else if (listItemType == ListItemType.EditItem)
{
TextBox textBox = new TextBox();
textBox.DataBinding += new EventHandler(textBox_DataBinding);
container.Controls.Add(textBox);
}
else if (listItemType == ListItemType.Header)
{
Literal literal = new Literal();
literal.Text = value1;
container.Controls.Add(literal);
}
else if (listItemType == ListItemType.Footer)
{
TextBox textBox = new TextBox();
container.Controls.Add(textBox);
}
}
private void textBox_DataBinding(object sender, EventArgs e)
{
TextBox textBox = (TextBox)(sender);
GridViewRow row = (GridViewRow)(textBox.NamingContainer);
textBox.Text = DataBinder.Eval(row.DataItem, value1).ToString();
}
}
How do I use commands in a GridView with Dynamically added columns? What is wrong with my code?
Thank you!

Answer 1

Dynamically added controls must be added on each post, you can't just add these controls on the first page load. Try removing your BindGridData() from within the Page.IsPostBack == false.