User Login in ASP.Net using C# with session

 HTML Markup  
 The HTML markup consists of an ASP.Net Login control for which the OnAuthenticate event handler has been specified.  
 <form id="form1" runat="server">  
 <asp:Login ID = "Login1" runat = "server" OnAuthenticate= "ValidateUser"></asp:Login>  
 </form>  

 Namespaces  
 You will need to import the following namespaces.  
 using System.Data;  
 using System.Configuration;  
 using System.Data.SqlClient;  
 using System.Web.Security;  
 Stored Procedure to Validate the User Credentials  
 The following stored procedure is used to validate the user credentials, this stored procedure first checks whether the username and password are correct else returns -1.  
 If the username and password are correct but the user has not been activated then the code returned is -2.  
 If the username and password are correct and the user account has been activated then UserId of the user is returned by the stored procedure.  
 CREATE PROCEDURE [dbo].[Validate_User]  
    @Username NVARCHAR(20),  
    @Password NVARCHAR(20)  
 AS  
 BEGIN  
    SET NOCOUNT ON;  
    DECLARE @UserId INT, @LastLoginDate DATETIME  
    SELECT @UserId = UserId, @LastLoginDate = LastLoginDate  
    FROM Users WHERE Username = @Username AND [Password] = @Password  
    IF @UserId IS NOT NULL  
    BEGIN  
       IF NOT EXISTS(SELECT UserId FROM UserActivation WHERE UserId = @UserId)  
       BEGIN  
          UPDATE Users  
          SET LastLoginDate = GETDATE()  
          WHERE UserId = @UserId  
          SELECT @UserId [UserId] -- User Valid  
       END  
       ELSE  
       BEGIN  
          SELECT -2 -- User not activated.  
       END  
    END  
    ELSE  
    BEGIN  
       SELECT -1 -- User invalid.  
    END  
 END  
 Validating the User Credentials  
 The below event handler gets called when the Log In button is clicked. Here the Username and Password entered by the user is passed to the stored procedure and its status is captured and if the value is not -1 (Username or password incorrect) or -2 (Account not activated) then the user is redirected to the Home page using FormsAuthentication RedirectFromLoginPage method.  
 protected void ValidateUser(object sender, EventArgs e)  
 {  
   int userId = 0;  
   string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;  
   using (SqlConnection con = new SqlConnection(constr))  
   {  
     using (SqlCommand cmd = new SqlCommand("Validate_User"))  
     {  
       cmd.CommandType = CommandType.StoredProcedure;  
       cmd.Parameters.AddWithValue("@Username", Login1.UserName);  
       cmd.Parameters.AddWithValue("@Password", Login1.Password);  
       cmd.Connection = con;  
       con.Open();  
       userId = Convert.ToInt32(cmd.ExecuteScalar());  
       con.Close();  
     }  
     switch (userId)  
     {  
       case -1:  
         Login1.FailureText = "Username and/or password is incorrect.";  
         break;  
       case -2:  
         Login1.FailureText = "Account has not been activated.";  
         break;  
       default:  
         FormsAuthentication.RedirectFromLoginPage(Login1.UserName, Login1.RememberMeSet);  
         break;  
     }  
   }  
 }  
 Home Page  
 After successful login user will be redirected to this page.  
 HTML Markup  
 In this page I have made use of ASP.Net LoginName control to display the name of the Logged In user and LoginStatus control to allow user Logout.  
 <div>  
   Welcome  
   <asp:LoginName ID="LoginName1" runat="server" Font-Bold = "true" />  
   <br />  
   <br />  
   <asp:LoginStatus ID="LoginStatus1" runat="server" />  
 </div>  
 Namespaces  
 You will need to import the following namespaces.  
 using System.Web.Security;  
 Verify whether User has Logged In  
 Inside the Page Load event, first we verify whether the User is authenticated using the IsAuthenticated property. If the user is not authenticated then he is redirected back to the Login page using FormsAuthentication RedirectToLoginPage method.  
 protected void Page_Load(object sender, EventArgs e)  
 {  
   if (!this.Page.User.Identity.IsAuthenticated)  
   {  
     FormsAuthentication.RedirectToLoginPage();  
   }  
 }  
 Web.Config Configuration  
 You will need to add the following configuration in the Web.Config file in the <system.web> section.  
 <authentication mode="Forms">  
  <formsdefaultUrl="~/Home.aspx" loginUrl="~/Login.aspx" slidingExpiration="true" timeout="2880"></forms>  
 </authentication>