Introduction:
In this article I will show you
that how you can validate the controls which are inside the GridView control.
For this I will make the editable GridView and use the RequiredFieldValidator
for the TextBoxes. I will also show you that how you can use validation against
the DropDownList control which is contained inside the GridView control.
Populating the GridView
Control:
Our first task is to populate the
GridView control. Let's first see the HTML code of the GridView control so that
you will have the idea of what the GridView looks like:
| <asp:GridView
ID="GridView1"
runat="server"
AutoGenerateColumns="False"
OnRowCancelingEdit="GridView1_RowCancelingEdit"
OnRowEditing="GridView1_RowEditing"
OnRowUpdating="GridView1_RowUpdating"
OnRowDataBound="GridView1_RowDataBound"
Font-Names="Arial"
Font-Size="Small">
<Columns>
<asp:BoundField
DataField="CategoryID"
HeaderText="CategoryID"
/>
<asp:BoundField
DataField="CategoryName"
HeaderText="CategoryName"
/>
<asp:TemplateField
HeaderText="Description">
<ItemTemplate>
<asp:Label
ID="Label1"
Text='<%#
Eval("Description") %>'
runat="server"
Font-Names="Arial"></asp:Label> <br
/>
<br
/>
</ItemTemplate>
<EditItemTemplate>
<asp:RequiredFieldValidator
ErrorMessage="This
field cannot be blank"
ControlToValidate="TextBox1"
ID="RequiredFieldValidator1"
runat="server"></asp:RequiredFieldValidator>
<asp:TextBox
ID="TextBox1"
Width="98%"
Text='<%#
Eval("Description") %>'
runat="server"></asp:TextBox>
</EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField
HeaderText="Choose">
<ItemTemplate>
<asp:DropDownList
ID="DropDownList1"
DataSource='<%#
PopulateDropDownList() %>'
DataTextField="CategoryName"
DataValueField="CategoryName"
runat="server"
Width="116px">
</asp:DropDownList><br
/>
<asp:RequiredFieldValidator
ID="RequiredFieldValidator2"
runat="server"
ControlToValidate="DropDownList1"
ErrorMessage="Please Select the Item"
InitialValue="Select
an item"></asp:RequiredFieldValidator>
</ItemTemplate>
</asp:TemplateField>
<asp:CommandField
ShowEditButton="True"
/>
</Columns>
</asp:GridView>
|
As you can see that two BoundColumns and two
TemplateColumns. The CategoryID and Category Name are the Bound columns which
are bound to the "CategoryID" and "CategoryName" fields in the Categories table
in Northwind Database. The "Description" and "Choose" columns are template
columns. The GridView looks something like this:
If you carefully read the HTML code of the
GridView which I have posted above then you will notice one very special thing.
The RequiredFieldValidator for the TextBox control in the Description column is
placed in the EditItemTemplate of the GridView control. This is because the
TextBox is in the EditItemTemplate and that is what we need to validate. If you
put the RequiredFieldValidator in any ItemTemplate or any other Template
supported by GridView you will recieve an error saying that GridView is unable
to find the control to validate.
I have done the same thing with the
DropDownList. Since the DropDownList is in the ItemTemplate of the GridView
control so I placed the RequiredFieldValidator inside the ItemTemplate right
beneath the DropDownList control.
It is a common scenario that you want the first
item of the DropDownList to be some message saying "Please select an item". For
this you can add the item dynamically inside the GridView_RowDataBound event.
|
protected
void
GridView1_RowDataBound(object
sender, GridViewRowEventArgs
e) {
if
(e.Row.RowType == DataControlRowType.DataRow)
{
DropDownList ddList = (DropDownList)e.Row.FindControl("DropDownList1");
ddList.Items[0].Text =
"Select an item";
ddList.Items[0].Value =
"Select an item";
}
} |
Don't forget to assign the value property of
the DropDownList to "Select an item" or any other text you like. It is this
value that is compared against a RequiredFieldValidator. Now, you can easily set
the RequiredFieldValidator's InitialValue property to "Select an item" or
whatever your text was which means that you cannot leave the control whose value
or text property is "Select an item" or the text set by you.
| <asp:RequiredFieldValidator
ID="RequiredFieldValidator2"
runat="server"
ControlToValidate="DropDownList1"
ErrorMessage="Select
the Item"
InitialValue="Select an item"></asp:RequiredFieldValidator> |
You will also notice that when you loose focus
from the control the validation control event will be fired. This is because the
validation controls have a property "EnableClientScript" which means that the
validation will be fired on the client side first and then on the server side.
If you set EnableClientScript = false then client validation won't be fired and
the validation control will wait for Page.Validate event to occur. If
Page.Validate does not occur then no validation will be fired.
It is a good idea to keep EnableClientScript
enabled so validation can be fired both on the client side as well as the server
side.
I have attached the source code for this
project. Please feel free to download it.
I hope you liked this article, happy coding!
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Export Button is a custom control that let's you export your
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