Thread: Programmatically Add Item to Validation Summary

I had an instance where I wanted to simply set off ASP.Net's ValidationSummary control to display an error to the user instead of creating another element to handle this. After some research, I came across the IValidator class.

Code:

Imports System.Web.UI
    Public Class ValidationError
        Implements IValidator
        Private _errorMessage As String = String.Empty
        Private _isValid As Boolean = False
        Public Shared Sub Display(ByVal message As String)
            Dim currentPage As Page = TryCast(HttpContext.Current.Handler, Page)
            currentPage.Validators.Add(New ValidationError(message))
        End Sub
        Public Sub New(ByVal message As String)
            ErrorMessage = message
            IsValid = False
        End Sub
        Public Property ErrorMessage() As String Implements System.Web.UI.IValidator.ErrorMessage
            Get
                Return _errorMessage
            End Get
            Set(ByVal value As String)
                _errorMessage = value
            End Set
        End Property
        Public Property IsValid() As Boolean Implements System.Web.UI.IValidator.IsValid
            Get
                Return _isValid
            End Get
            Set(ByVal value As Boolean)
                _isValid = value
            End Set
        End Property
        Public Sub Validate() Implements System.Web.UI.IValidator.Validate
        End Sub
    End Class

To call this, simply do the following:

Code:

Page.Validate()
ValidationError.Display("Place error message here")

Hi,

here is a simpler solution. Create a control that derives from BaseValidator. Implement the abstract EvaluateIsValid method. Make sure that the ControlPropertiesValid() method always returns true because there is no control to validate and set Display to ValidatorDisplay.None to prevent this control from displaying error text at its position in the HTML code.

Here is the complete C# code:

Code:

    [ToolboxData("<{0}:ValidationError runat=server />")]
    public class ValidationError : BaseValidator
    {
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            ErrorMessage = ""; // Clear error message
            /*
             * Prevent this control from displaying error text.
             * This will be done in a ValidationSummary control.
             */
            base.Display = ValidatorDisplay.None;
        }

        protected override void OnPreRender(EventArgs e)
        {
            /*
             * Make the control check the ErrorMessage
             */
            EvaluateIsValid(); 
            base.OnPreRender(e);
        }

        protected override bool ControlPropertiesValid()
        {
            /*
             * This is always true because no control should be checked.
             */
            return true; 
        }

        protected override bool EvaluateIsValid()
        {
            /*
             * Invalid if any not empty error message has been set.
             */
            base.IsValid = (ErrorMessage == null) || (ErrorMessage == "");
            return base.IsValid;
        }
    }

To call this control, put it onto the page, and set theErrorMessage property in the code if required:

Code:

            try
            {
                ...
                ...
                ...
            }
            catch (Exception ex)
            {
                ValidationError.ErrorMessage = ex.Message;
            }