Here, we see how to use Page.IsValid property
in VB.NET. ASP.net ships with a couple of validator controls that allow you to
determine whether the value of the input controls they are validating is valid.
The Page.IsValid property tells you indicating whether page validation
succeeded. True if page validation succeeded otherwise false.
Example
If the property returns true, the Text property
of the Output control is set to "Page is valid!" Otherwise, it is set to "Some
of the required fields are empty.
Page.Validate()
If (Page.IsValid) Then
lblOutput.Text = "Page is Valid!"
Else
lblOutput.Text = "Some required fields are empty."
End If
It can be called only after the Page.Validate method is called. By using
this property, you can add logic to your page to determine whether to proceed
with the PostBack event or not. So, in addition to relying on client side
validation, it is also important that you call Page.IsValid when handling the
postback event.
For Example
In this example we will see what happened when
we click on the Button2.
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="TextBox1" runat="server" ValidationGroup="MyValidationGroup"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="TextBox1"
ErrorMessage="This
field is
required!" ValidationGroup="MyValidationGroup"></asp:RequiredFieldValidator>
<br />
<asp:Button ID="Button1" runat="server" Text="Button1" ValidationGroup="MyValidationGroup"
CausesValidation="true" />
<br />
<br />
<asp:TextBox ID="TextBox2" runat="server" ValidationGroup="AnotherValidationGroup"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="TextBox2"
ErrorMessage="This
field is
required!" ValidationGroup="AnotherValidationGroup"></asp:RequiredFieldValidator>
<br />
<asp:Button ID="Button2" runat="server" Text="Button2" ValidationGroup="AnotherValidationGroup"
OnClick="Button2_Click" />
</div>
</form>
</body>
Now double click on the Button2 and add the
following code.
Protected Sub Button2_Click(ByVal
sender As Object,
ByVal e As EventArgs)
Page.Validate("MyValidationGroup")
If Not
Page.IsValid Then
Return
End If
Response.Write("Button
was clicked at " & DateTime.Now.ToShortTimeString())
End Sub
Now run the application and enter some value in
TextBoxes.
Figure1
Now click on the Button2.
Figure2