ASP.NET

public class BasicAuthMessageHandler : DelegatingHandler
{
    private const string BasicAuthResponseHeader = "WWW-Authenticate";
    private const string BasicAuthResponseHeaderValue = "Basic";

    [Inject]
    public iUser Repository { get; set; }
    
    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        AuthenticationHeaderValue authValue = request.Headers.Authorization;
        if (authValue != null && !String.IsNullOrWhiteSpace(authValue.Parameter))
        {
            api_login parsedCredentials = ParseAuthorizationHeader(authValue.Parameter);
            if (parsedCredentials != null)
            {
                IPrincipal principal;
                if (TryGetPrincipal(parsedCredentials.username, parsedCredentials.password, out principal))
                {
                    Thread.CurrentPrincipal = principal;
                }
            }
        }
        
        return base.SendAsync(request, cancellationToken).ContinueWith(task =>
        {
            var response = task.Result;
            if (response.StatusCode == HttpStatusCode.Unauthorized && !response.Headers.Contains(BasicAuthResponseHeader))
            {
                response.Headers.Add(BasicAuthResponseHeader, BasicAuthResponseHeaderValue);
            }
            
            return response;
        });
    }
    
    private api_login ParseAuthorizationHeader(string authHeader)
    {
        string[] credentials = Encoding.ASCII.GetString(Convert.FromBase64String(authHeader)).Split(new[] { ':' });
        if (credentials.Length != 2 || string.IsNullOrEmpty(credentials[0]) || string.IsNullOrEmpty(credentials[1])) return null;

        return new api_login()
        {
            username = credentials[0],
            password = credentials[1],
        };
    }
    
    private bool TryGetPrincipal(string userName, string password, out IPrincipal principal)
    {
        // this is the method that authenticates against my repository (in this case, hard coded)
        // you can replace this with whatever logic you'd use, but proper separation would put the
        // data access in a repository or separate layer/library.
        api_login user = Repository.Validate2(userName, password);
        
        if (user != null)
        {
            // once the user is verified, assign it to an IPrincipal with the identity name and applicable roles
            principal = new GenericPrincipal(new GenericIdentity(user.username));
            return true;
        }
        
        principal = null;
        return false;
    } 
}

private bool TryGetPrincipal(string userName, string password, out IPrincipal principal)
        {

            api_login user = Repository.Validate2(userName, password);

            if (user.username != null)
            {
                // once the user is verified, assign it to an IPrincipal with the identity name and applicable roles
                principal = new GenericPrincipal(new GenericIdentity(user.username));
               // principal = new GenericPrincipal(new GenericIdentity(user.username), System.Web.Security.Roles.GetRolesForUser(user.role));
               
                return true;
            }

            principal = null;
            return false;
        }
    }

principal = new GenericPrincipal(new GenericIdentity(user.username), null);

private bool TryGetPrincipal(string userName, string password, out IPrincipal principal)
{

    // data access in a repository or separate layer/library.
    api_login user = repository.Validate2(userName, password);

   // int failedAttempts = 0;
    if (user.username != null)
    {
        // once the user is verified, assign it to an IPrincipal with the identity name and applicable roles
        //failedAttempts += 1;
        principal = new GenericPrincipal(new GenericIdentity(user.username), null);
    }

    else if (user.username == null)
    {
        //throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.NotFound, String.Format("this identity does not exist")));

        throw new HttpResponseException(HttpStatusCode.Unauthorized);

    }
    principal = null;

    return false;
}

public class BasicAuthHandler : DelegatingHandler
    {

        private const string BasicAuthResponseHeader = "WWW-Authenticate";
        private const string BasicAuthResponseHeaderValue = "Basic";

        //private readonly iUser repository;

        public BasicAuthHandler(iUser repository)
        {
            this.repository = repository;
        }

        [Inject]
        iUser repository { get; set; }


        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            AuthenticationHeaderValue authValue = request.Headers.Authorization;


            if (authValue == null || authValue.Scheme != BasicAuthResponseHeaderValue)
            {
                return Unauthorized(request);
            }
            string[] credentials = Encoding.ASCII.GetString(Convert.FromBase64String(authValue.Parameter)).Split(new[] { ':' });
            if (credentials.Length != 2 || string.IsNullOrEmpty(credentials[0]) || string.IsNullOrEmpty(credentials[1]))
            {
                return Unauthorized(request);
           
            }
            api_login user = repository.Validate2(credentials[0], credentials[1]);
            if (user == null)
            {
                return Unauthorized(request);
            }
            IPrincipal principal = new GenericPrincipal(new GenericIdentity(user.username, BasicAuthResponseHeaderValue), null);
            Thread.CurrentPrincipal = principal;
            HttpContext.Current.User = principal;

            return base.SendAsync(request, cancellationToken);
        }

        private Task<HttpResponseMessage> Unauthorized(HttpRequestMessage request)
        {
            var response = request.CreateResponse(HttpStatusCode.Unauthorized);
            response.Headers.Add(BasicAuthResponseHeader, BasicAuthResponseHeaderValue);
            var task = new TaskCompletionSource<HttpResponseMessage>();
            task.SetResult(response);
            return task.Task;
        }

        private api_login ParseAuthorizationHeader(string authHeader)
        {
            string[] credentials = Encoding.ASCII.GetString(Convert.FromBase64String(authHeader)).Split(new[] { ':' });
            if (credentials.Length != 2 || string.IsNullOrEmpty(credentials[0]) || string.IsNullOrEmpty(credentials[1])) return null;

            return new api_login()
            {
                username = credentials[0],
                password = credentials[1],
            };
        }

        private bool TryGetPrincipal(string userName, string password, out IPrincipal principal)
        {

            // data access in a repository or separate layer/library.
            api_login user = repository.Validate2(userName, password);

           // int failedAttempts = 0;
            if (user.username != null)
            {
                // once the user is verified, assign it to an IPrincipal with the identity name and applicable roles
                //failedAttempts += 1;
                principal = new GenericPrincipal(new GenericIdentity(user.username), null);
            }

            else if (user.username == null)
            {
                //throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.NotFound, String.Format("this identity does not exist")));
                
                throw new HttpResponseException(HttpStatusCode.Unauthorized);
               
            }
            principal = null;

            return false;
        }
           
    }

• You've added a validator to a control.
• You've entered invalid data in the control.
• The validator is now telling you that the data you've entered is invalid.

Dim tbl As New DataTable
tbl.Columns.Add("Period", GetType(String))
tbl.Columns.Add("Item", GetType(String))
Dim entry As DataRow = tbl.NewRow
entry("Period") = "7.30-8.30"
entry("Item") = "sub1"
entry = tbl.NewRow
entry("Period") = "8.30-9.30"
entry("Item") = "sub2"

Me.GridView1.AutoGenerateColumns = True
Me.GridView1.DataSource = tbl
Me.GridView1.DataBind()