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How to login users programmatically in asp.net

Login user programmatically
In .net framework Membership class’s ValidateUser() method allows us to programmatically verify the supplied username and password are valid. The Membership class’s ValidateUser(username, password) method exists under the System.Web.Security namespace. This method requires passing two parameters.

The first parameter name is 'username' and another parameter name is 'password'. Both parameters’ data type is String. The username parameter value passes the name of the user to be validated and the password parameter value passes the password for the specified user. If the username parameter is null or empty then this method throws an HttpException.

This method returns a Boolean value. If the supplied username and password are valid then it returns True, otherwise, it returns false.

In this example code, we manually build a login page without Login server control. This login page contains two TextBoxes and a submit Button. Two TextBoxes uses to collect the user's username and password. Submit Button posts the form to the webserver to verify the user's credentials. This asp.net application is configured to use forms authentication and Membership class.

If the login form's supplied user credentials are invalid then login failed and a login failure message displays to the user. If the supplied credentials are valid then the user logged in programmatically and the user will be redirected to the originally requested URL.

FormsAuthentication class’s RedirectFromLoginPage() method allows us to redirect an authenticated user back to the originally requested URL or the default URL.

The following asp.net c# example code demonstrates to us how we can programmatically log in a user in an asp.net application.
Login.aspx

<%@ Page Language="C#" %>

<!DOCTYPE html>

<script runat="server">
    protected void Button1_Click(object sender, System.EventArgs e) {
        if (Membership.ValidateUser(TextBox1.Text.ToString(), TextBox2.Text.ToString()))
        {
            FormsAuthentication.RedirectFromLoginPage(TextBox1.Text.ToString(), false);
        }
        else {
            Response.Write("Input correct User Name and Password!");
        }
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Login Example: how to login users programmatically in asp.net</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Label ID="Label1" runat="server" Text="User Name" AssociatedControlID="TextBox1"></asp:Label>
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
        <br />
        <asp:Label ID="Label2" runat="server" Text="Password" AssociatedControlID="TextBox2"></asp:Label>
        <asp:TextBox ID="TextBox2" runat="server" TextMode="Password"></asp:TextBox>
        <br />
        <asp:Button ID="Button1" runat="server" Text="Login" OnClick="Button1_Click" />
    </div>
    </form>
</body>
</html>
Default.aspx

<%@ Page Language="C#" %>

<!DOCTYPE html>

<script runat="server">

</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>Programmatically login example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h1>Are you Logged in?</h1>
        <asp:LoginStatus ID="LoginStatus1" runat="server" />
        <br /><br />
        <asp:LoginName ID="LoginName2" runat="server" FormatString="Hi {0}! you are logged in." Font-Size="X-Large" ForeColor="DarkCyan" />
    </div>
    </form>
</body>

</html>
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