Avoid (Prevent) Page refresh (PostBack) after TextBox TextChanged in ASP.Net

Hi rakeshkuma,

Check this example. Now please take its reference and correct your code.

HTML

<asp:ScriptManager runat="server" />
<asp:UpdatePanel ID="UpdatePanel2" runat="server">
    <ContentTemplate>
        <asp:TextBox ID="txtsuno" runat="server" AutoPostBack="True" OnTextChanged="txtsuno_TextChanged"></asp:TextBox>
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="txtsuno" EventName="TextChanged" />
    </Triggers>
</asp:UpdatePanel>

Code

C#

protected void txtsuno_TextChanged(object sender, EventArgs e)
{
    ScriptManager.RegisterClientScriptBlock(UpdatePanel2, this.GetType(), "", "alert('" + txtsuno.Text + "')", true);
}

VB.Net

Protected Sub txtsuno_TextChanged(ByVal sender As Object, ByVal e As EventArgs)
    ScriptManager.RegisterClientScriptBlock(UpdatePanel2, Me.GetType(), "", "alert('" & txtsuno.Text & "')", True)
End Sub

Screenshot