How to set disable or readonly in a datagrid view - asp.net

Question

I have the following datagrid view that is data bound with some data at the DB
I need to load the information in the data grid and make all the textbox in some columns(in the example only comes on but there are many) to be readonly or disable.
<asp:DataGrid ID="grdRequestTypeItem" TabIndex="1" runat="server" CssClass="Grid" AutoGenerateColumns="False"
AllowSorting="True" Visible="true">
<SelectedItemStyle CssClass="GridSelectedItem"></SelectedItemStyle>
<AlternatingItemStyle CssClass="GridAlternatingItem"></AlternatingItemStyle>
<ItemStyle CssClass="GridItem"></ItemStyle>
<HeaderStyle CssClass="GridHeader"></HeaderStyle>
<Columns>
<asp:TemplateColumn HeaderText="Lot Number">
<ItemTemplate >
<asp:TextBox ID="txtLot" runat="server" Width="100%" Text='<%# DataBinder.Eval(Container, "DataItem.Lot") %>' />
</ItemTemplate>
</asp:TemplateColumn>
</Columns>
</asp:DataGrid>
How can I disable that column in the code behind ??
Neither of the following are working
grdRequestTypeItem.Columns[1].IsReadOnly = true;
((BoundField)grdRequestTypeItem.Columns[0]).ReadOnly = true;
((TemplateField)grdRequestTypeItem.Columns[0]).EditItemTemplate = null;

Answer 1

Even if your DataGrid is not in EditMode it displays the TextBox inside the ItemTemplate. Otherwise you use an EditItemTemplate. That's why neither of your solutions work. You have several options:
Put a <asp:Literal> Control into your ItemTemplate
Bind the ReadOnly property of the TextBox to a bool value of your viewModel
from code behind, you have to address the correct control
you could use something like this to reference the textbox within the item template
foreach (GridViewRow row in grdRequestTypeItem.Rows)
{
var txtLot = row.FindControl("txtLot") as TextBox;
txtLog.IsReadOnly = true;
}
You could also use the DataBinding Event on the row instead of looping through the rows like in the answer of #Stealth22

Answer 2

Try this:
<asp:DataGrid ID="grdRequestTypeItem" TabIndex="1" runat="server" CssClass="Grid" AutoGenerateColumns="False" AllowSorting="True" Visible="true"
OnItemDataBound="grdRequestTypeItem_ItemBound">
And then in your code-behind...
protected void grdRequestTypeItem_ItemBound(Object sender, DataGridItemEventArgs e)
{
if((e.Item.ItemType == ListItemType.Item) || (e.Item.ItemType == ListItemType.AlternatingItem))
{
TextBox txtLot = e.Item.FindControl("txtLot");
if (txtLot != null)
{
txtLot.ReadOnly = true;
}
}
}
Someone can correct me if I am wrong anywhere, as I work more with GridViews than DataGrids, but as far as I know, the principle is the same.