User Input Validations using ErrorProvider in VB.NET
This article and attached project demonstrates how to use the ErrorProvider component in Windows Forms and VB.NET to implement user input validations.
User Input Validations in Windows Forms
Now, I am going to create an application in Windows Forms that uses the ErrorProvider component for implementing user input validations and display proper error messages when the data is invalid.
I have a Windows Forms application that looks like following and has two input controls. One is Author Name TextBox and the second is Age NumericUpDown control.
My goal here is to display error messages on the Submit Data button click event handler when Author Name is not specified and age is less than 21.
For this, I add two ErrorProvider components to the Form by dragging and dropping them from the ToolBox to the Form. I change their names to NameErrorProvider and AgeErrorProvider. Now, on the Button click event handler, I validate name and age and if the data is not valid, I display error messages in the ErrorProviders by calling the ErrorProvider.SetError method.
The complete code is listed below.
Public Class Form1
Private Sub SubmitButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SubmitButton.Click
' Validate Author Name
Dim err As String = ValidateAuthorName(AuthorNameTextBox.Text)
If (err = String.Empty) Then
NameErrorProvider.SetError(AuthorNameTextBox, "")
Else
NameErrorProvider.SetError(AuthorNameTextBox, err)
End If
' Validate Author Age
err = ValidateAuthorAge(AuthorAgeUpDown.Value)
If (err = String.Empty) Then
AgeErrorProvider.SetError(AuthorAgeUpDown, "")
Else
AgeErrorProvider.SetError(AuthorAgeUpDown, err)
End If
End Sub
''' <summary>
''' Verifies author name
''' </summary>
''' <returns></returns>
''' <remarks></remarks>
Private Function ValidateAuthorName(ByVal name As String) As String
Dim errorMessage As String = String.Empty
If name.Length <= 0 Then
errorMessage = "Author name is required."
End If
Return errorMessage
End Function
''' <summary>
''' Verifies author age
''' </summary>
''' <returns></returns>
''' <remarks></remarks>
Private Function ValidateAuthorAge(ByVal age As Int16) As String
Dim errorMessage As String = String.Empty
If age < 21 Then
errorMessage = "Age must be less than 21."
End If
Return errorMessage
End Function
End Class
Now when you run the application and provide invalid data and click Submit Data button, you will see ErrorProviders appear like following and rollover on them displays the error messages.
Summary
In this article, we saw how we can take advantages of built-in component in Windows Forms to provide user input validation functionality. Download the attached project for more details.