how to use RequiredFieldValidator control example in asp.net

RequiredFieldValidator is actually simple example, You can use it to make sure that the user has entered something in a TextBox control. Let's give it a try, and add a RequiredFieldValidator in  asp.net  to our page. We will also add a TextBox to validate, as well as a button to submit the form with.

<form id="form1" runat="server">
    Your name:<br />
    <asp:TextBox runat="server" id="txtName" />
    <asp:RequiredFieldValidator runat="server" id="reqName" controltovalidate="txtName" errormessage="Please enter your name!" />
    <br />
    <asp:Button runat="server" id="btnSubmitForm" text="Ok" /> 

 </form>

Actually, that's all we need to test the most basic part of the RequiredFieldValidator. 

I'm sure that all the attributes of the controls makes sense by now, so I won't go into details about them. 

Try running the website and click the button. You should see something like this: 

 





Right now, the button does nothing, besides posting back if the page is valid. We will change this by adding an onclick event to it:

<asp:Button runat="server" id="btnSubmitForm" text="Ok" onclick="btnSubmitForm_Click" />

In the CodeBehind file, we add the following event handler: 

protected void btnSubmitForm_Click(object sender, EventArgs e)
{
    if(Page.IsValid)
    {
        btnSubmitForm.Text = "Form is valid!";
    }
}