Button is not fired normally and fired when UseSubmitBehavior="false" but textbox values are coming null
<p>I am using ASP button its working properly at client side but on server side its not firing.</p>

<pre><code>&lt;div style="text-align: center"&gt;
    &lt;div&gt;
        &lt;div id="UserName"&gt;
            &lt;b&gt;LoginName&lt;/b&gt;
            &lt;asp:TextBox ID="txt_LoginName" runat="server"&gt;&lt;/asp:TextBox&gt;
        &lt;/div&gt;
    &lt;/div&gt;
    &lt;div&gt;
         &lt;div id="Password"&gt;
             &lt;b&gt;Password&amp;nbsp;&amp;nbsp;&lt;/b&gt;
             &lt;asp:TextBox ID="txt_Password" TextMode="Password" runat="server"&gt;&lt;/asp:TextBox&gt;
         &lt;/div&gt;
    &lt;/div&gt;
    &lt;div style="text-align: right; width: 210px;"&gt;
        &lt;asp:Button ID="btn_SignIn" OnClientClick="LogInUser()" UseSubmitBehavior="false" runat="server" Text="Login`enter code here`" /&gt;
        &lt;asp:Label ID="lbl_InValidError" runat="server"&gt;&lt;/asp:Label&gt;
    &lt;/div&gt;
&lt;/div&gt; 
</code></pre>

<p>Client Side Code:</p>

<pre><code>    function LogInUser()
    {
        var LoginName = document.getElementById("&lt;%=txt_LoginName.ClientId %&gt;").value;
        var Password = document.getElementById("&lt;%=txt_Password.ClientId%&gt;").value;

        if(LoginName == '')
        {
            alert("Please Enter UserName.");
            return false;
        }
        else
        {
            if(Password == '')
            {
                alert("Please Enter Password.");
                return false;
            }
            else
            {
                alert("You are logged in");                   
            }
        }
        return true;
    }
</code></pre>

<p>Server Side Code</p>

<pre><code>Protected Sub btn_SignIn_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn_SignIn.Click
 If Trim(Me.txt_LoginName.Text) = "" Then
            lbl_InValidError.Text = "Please Enter Login Name."
            Return
        End If
        If txt_Password.Text = "" Then
            lbl_InValidError.Text = "Please Enter Password."
            Return
        End If
End Sub
</code></pre>

<p>when I am not using <code>UseSubmitBehavior=false</code> event is not fire at server side.</p>
