ErrorProvider.SetError(Control, String) ErrorProvider.SetError(Control, String) ErrorProvider.SetError(Control, String) Method

Definition

Sets the error description string for the specified control.

public:
 void SetError(System::Windows::Forms::Control ^ control, System::String ^ value);
public void SetError (System.Windows.Forms.Control control, string value);
member this.SetError : System.Windows.Forms.Control * string -> unit
Parameters
control
Control Control Control

The control to set the error description string for.

value
String String String

The error description string, or null or Empty to remove the error.

Exceptions

Examples

The following code example demonstrates using the ErrorProvider class to notify the user of a data entry error. The example creates a Form that contains a TextBox control, a NumericUpDown control, and a ComboBox control, each validating its content, and an ErrorProvider for each control. The example sets error icon options using the BlinkRate and BlinkStyle properties and the SetIconAlignment and SetIconPadding methods. The SetError method is called with or without appropriate error text during a control's Validated event, depending upon the content in the control.

#using <System.dll>
#using <System.Windows.Forms.dll>
#using <System.Drawing.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
public ref class Form1: public System::Windows::Forms::Form
{
private:
   System::Windows::Forms::Label ^ label1;
   System::Windows::Forms::Label ^ label2;
   System::Windows::Forms::Label ^ label4;
   System::Windows::Forms::Label ^ label5;
   System::Windows::Forms::Label ^ label6;
   System::Windows::Forms::Label ^ label3;
   System::Windows::Forms::TextBox^ nameTextBox1;
   System::Windows::Forms::NumericUpDown^ ageUpDownPicker;
   System::Windows::Forms::ComboBox^ favoriteColorComboBox;
   System::Windows::Forms::ErrorProvider^ ageErrorProvider;
   System::Windows::Forms::ErrorProvider^ nameErrorProvider;
   System::Windows::Forms::ErrorProvider^ favoriteColorErrorProvider;

public:
   Form1()
   {
      this->nameTextBox1 = gcnew System::Windows::Forms::TextBox;
      this->label1 = gcnew System::Windows::Forms::Label;
      this->label2 = gcnew System::Windows::Forms::Label;
      this->ageUpDownPicker = gcnew System::Windows::Forms::NumericUpDown;
      this->favoriteColorComboBox = gcnew System::Windows::Forms::ComboBox;
      this->label3 = gcnew System::Windows::Forms::Label;
      this->label4 = gcnew System::Windows::Forms::Label;
      this->label5 = gcnew System::Windows::Forms::Label;
      this->label6 = gcnew System::Windows::Forms::Label;
      
      // Name Label
      this->label1->Location = System::Drawing::Point( 56, 32 );
      this->label1->Size = System::Drawing::Size( 40, 23 );
      this->label1->Text = "Name:";
      
      // Age Label
      this->label2->Location = System::Drawing::Point( 40, 64 );
      this->label2->Size = System::Drawing::Size( 56, 23 );
      this->label2->Text = "Age (3-5)";
      
      // Favorite Color Label
      this->label3->Location = System::Drawing::Point( 24, 96 );
      this->label3->Size = System::Drawing::Size( 80, 24 );
      this->label3->Text = "Favorite color";
      
      // ErrorBlinkStyle::AlwaysBlink Label
      this->label4->Location = System::Drawing::Point( 264, 32 );
      this->label4->Size = System::Drawing::Size( 160, 23 );
      this->label4->Text = "ErrorBlinkStyle::AlwaysBlink";
      
      // ErrorBlinkStyle::BlinkIfDifferentError Label
      this->label5->Location = System::Drawing::Point( 264, 64 );
      this->label5->Size = System::Drawing::Size( 200, 23 );
      this->label5->Text = "ErrorBlinkStyle::BlinkIfDifferentError";
      
      // ErrorBlinkStyle::NeverBlink Label
      this->label6->Location = System::Drawing::Point( 264, 96 );
      this->label6->Size = System::Drawing::Size( 200, 23 );
      this->label6->Text = "ErrorBlinkStyle::NeverBlink";
      
      // Name TextBox
      this->nameTextBox1->Location = System::Drawing::Point( 112, 32 );
      this->nameTextBox1->Size = System::Drawing::Size( 120, 20 );
      this->nameTextBox1->TabIndex = 0;
      this->nameTextBox1->Validated += gcnew System::EventHandler( this, &Form1::nameTextBox1_Validated );
      
      // Age NumericUpDown
      this->ageUpDownPicker->Location = System::Drawing::Point( 112, 64 );
      array<int>^temp0 = {150,0,0,0};
      this->ageUpDownPicker->Maximum = System::Decimal( temp0 );
      this->ageUpDownPicker->TabIndex = 4;
      this->ageUpDownPicker->Validated += gcnew System::EventHandler( this, &Form1::ageUpDownPicker_Validated );
      
      // Favorite Color ComboBox
      array<Object^>^temp1 = {"None","Red","Yellow","Green","Blue","Purple"};
      this->favoriteColorComboBox->Items->AddRange( temp1 );
      this->favoriteColorComboBox->Location = System::Drawing::Point( 112, 96 );
      this->favoriteColorComboBox->Size = System::Drawing::Size( 120, 21 );
      this->favoriteColorComboBox->TabIndex = 5;
      this->favoriteColorComboBox->Validated += gcnew System::EventHandler( this, &Form1::favoriteColorComboBox_Validated );
      
      // Set up how the form should be displayed and add the controls to the form.
      this->ClientSize = System::Drawing::Size( 464, 150 );
      array<System::Windows::Forms::Control^>^temp2 = {this->label6,this->label5,this->label4,this->label3,this->favoriteColorComboBox,this->ageUpDownPicker,this->label2,this->label1,this->nameTextBox1};
      this->Controls->AddRange( temp2 );
      this->Text = "Error Provider Example";
      
      // Create and set the ErrorProvider for each data entry control.
      nameErrorProvider = gcnew System::Windows::Forms::ErrorProvider;
      nameErrorProvider->SetIconAlignment( this->nameTextBox1, ErrorIconAlignment::MiddleRight );
      nameErrorProvider->SetIconPadding( this->nameTextBox1, 2 );
      nameErrorProvider->BlinkRate = 1000;
      nameErrorProvider->BlinkStyle = System::Windows::Forms::ErrorBlinkStyle::AlwaysBlink;
      ageErrorProvider = gcnew System::Windows::Forms::ErrorProvider;
      ageErrorProvider->SetIconAlignment( this->ageUpDownPicker, ErrorIconAlignment::MiddleRight );
      ageErrorProvider->SetIconPadding( this->ageUpDownPicker, 2 );
      ageErrorProvider->BlinkStyle = System::Windows::Forms::ErrorBlinkStyle::BlinkIfDifferentError;
      favoriteColorErrorProvider = gcnew System::Windows::Forms::ErrorProvider;
      favoriteColorErrorProvider->SetIconAlignment( this->favoriteColorComboBox, ErrorIconAlignment::MiddleRight );
      favoriteColorErrorProvider->SetIconPadding( this->favoriteColorComboBox, 2 );
      favoriteColorErrorProvider->BlinkRate = 1000;
      favoriteColorErrorProvider->BlinkStyle = System::Windows::Forms::ErrorBlinkStyle::NeverBlink;
   }


private:

   void nameTextBox1_Validated( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      if ( IsNameValid() )
      {
         
         // Clear the error, if any, in the error provider.
         nameErrorProvider->SetError( this->nameTextBox1, String.Empty );
      }
      else
      {
         
         // Set the error if the name is not valid.
         nameErrorProvider->SetError( this->nameTextBox1, "Name is required." );
      }
   }

   void ageUpDownPicker_Validated( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      if ( IsAgeTooYoung() )
      {
         
         // Set the error if the age is too young.
         ageErrorProvider->SetError( this->ageUpDownPicker, "Age not old enough" );
      }
      else
      if ( IsAgeTooOld() )
      {
         
         // Set the error if the age is too old.
         ageErrorProvider->SetError( this->ageUpDownPicker, "Age is too old" );
      }
      else
      {
         
         // Clear the error, if any, in the error provider.
         ageErrorProvider->SetError( this->ageUpDownPicker, String.Empty );
      }
   }

   void favoriteColorComboBox_Validated( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      if (  !IsColorValid() )
      {
         
         // Set the error if the favorite color is not valid.
         favoriteColorErrorProvider->SetError( this->favoriteColorComboBox, "Must select a color." );
      }
      else
      {
         
         // Clear the error, if any, in the error provider.
         favoriteColorErrorProvider->SetError( this->favoriteColorComboBox, String.Empty );
      }
   }


   // Functions to verify data.
   bool IsNameValid()
   {
      
      // Determine whether the text box contains a zero-length String*.
      return (nameTextBox1->Text->Length > 0);
   }

   bool IsAgeTooYoung()
   {
      
      // Determine whether the age value is less than three.
      return (ageUpDownPicker->Value < 3);
   }

   bool IsAgeTooOld()
   {
      
      // Determine whether the age value is greater than five.
      return (ageUpDownPicker->Value > 5);
   }

   bool IsColorValid()
   {
      
      // Determine whether the favorite color has a valid value.
      return ((favoriteColorComboBox->SelectedItem != 0) && ( !favoriteColorComboBox->SelectedItem->Equals( "None" )));
   }

};


[STAThread]
int main()
{
   Application::Run( gcnew Form1 );
}

using System;
using System.Drawing;
using System.Windows.Forms;

namespace ErrorProvider
{
    public class Form1 : System.Windows.Forms.Form
    {
        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.Label label2;
        private System.Windows.Forms.Label label4;
        private System.Windows.Forms.Label label5;
        private System.Windows.Forms.Label label6;
        private System.Windows.Forms.Label label3;
        private System.Windows.Forms.TextBox nameTextBox1;
        private System.Windows.Forms.NumericUpDown ageUpDownPicker;
        private System.Windows.Forms.ComboBox favoriteColorComboBox;
        private System.Windows.Forms.ErrorProvider ageErrorProvider;
        private System.Windows.Forms.ErrorProvider nameErrorProvider;
        private System.Windows.Forms.ErrorProvider favoriteColorErrorProvider;

        [STAThread]
        static void Main() 
        {
            Application.Run(new Form1());
        }

        public Form1()
        {
            this.nameTextBox1 = new System.Windows.Forms.TextBox();
            this.label1 = new System.Windows.Forms.Label();
            this.label2 = new System.Windows.Forms.Label();
            this.ageUpDownPicker = new System.Windows.Forms.NumericUpDown();
            this.favoriteColorComboBox = new System.Windows.Forms.ComboBox();
            this.label3 = new System.Windows.Forms.Label();
            this.label4 = new System.Windows.Forms.Label();
            this.label5 = new System.Windows.Forms.Label();
            this.label6 = new System.Windows.Forms.Label();

            // Name Label
            this.label1.Location = new System.Drawing.Point(56, 32);
            this.label1.Size = new System.Drawing.Size(40, 23);
            this.label1.Text = "Name:";

            // Age Label
            this.label2.Location = new System.Drawing.Point(40, 64);
            this.label2.Size = new System.Drawing.Size(56, 23);
            this.label2.Text = "Age (3-5)";           

            // Favorite Color Label
            this.label3.Location = new System.Drawing.Point(24, 96);
            this.label3.Size = new System.Drawing.Size(80, 24);
            this.label3.Text = "Favorite color";

            // ErrorBlinkStyle.AlwaysBlink Label
            this.label4.Location = new System.Drawing.Point(264, 32);
            this.label4.Size = new System.Drawing.Size(160, 23);
            this.label4.Text = "ErrorBlinkStyle.AlwaysBlink";

            // ErrorBlinkStyle.BlinkIfDifferentError Label
            this.label5.Location = new System.Drawing.Point(264, 64);
            this.label5.Size = new System.Drawing.Size(200, 23);
            this.label5.Text = "ErrorBlinkStyle.BlinkIfDifferentError";

            // ErrorBlinkStyle.NeverBlink Label
            this.label6.Location = new System.Drawing.Point(264, 96);
            this.label6.Size = new System.Drawing.Size(200, 23);
            this.label6.Text = "ErrorBlinkStyle.NeverBlink";

            // Name TextBox
            this.nameTextBox1.Location = new System.Drawing.Point(112, 32);
            this.nameTextBox1.Size = new System.Drawing.Size(120, 20);
            this.nameTextBox1.TabIndex = 0;
            this.nameTextBox1.Validated += new System.EventHandler(this.nameTextBox1_Validated);

            // Age NumericUpDown
            this.ageUpDownPicker.Location = new System.Drawing.Point(112, 64);
            this.ageUpDownPicker.Maximum = new System.Decimal(new int[] {150,0,0,0});
            this.ageUpDownPicker.TabIndex = 4;
            this.ageUpDownPicker.Validated += new System.EventHandler(this.ageUpDownPicker_Validated);

            // Favorite Color ComboBox
            this.favoriteColorComboBox.Items.AddRange(new object[] {"None","Red","Yellow",
                                                                    "Green","Blue","Purple"});
            this.favoriteColorComboBox.Location = new System.Drawing.Point(112, 96);
            this.favoriteColorComboBox.Size = new System.Drawing.Size(120, 21);
            this.favoriteColorComboBox.TabIndex = 5;
            this.favoriteColorComboBox.Validated += new System.EventHandler(this.favoriteColorComboBox_Validated);

            // Set up how the form should be displayed and add the controls to the form.
            this.ClientSize = new System.Drawing.Size(464, 150);
            this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                        this.label6,this.label5,this.label4,this.label3,
                                        this.favoriteColorComboBox,this.ageUpDownPicker,
                                        this.label2,this.label1,this.nameTextBox1});
            this.Text = "Error Provider Example";

            // Create and set the ErrorProvider for each data entry control.

            nameErrorProvider = new  System.Windows.Forms.ErrorProvider();
            nameErrorProvider.SetIconAlignment (this.nameTextBox1, ErrorIconAlignment.MiddleRight);
            nameErrorProvider.SetIconPadding (this.nameTextBox1, 2);
            nameErrorProvider.BlinkRate = 1000;
            nameErrorProvider.BlinkStyle = System.Windows.Forms.ErrorBlinkStyle.AlwaysBlink;

            ageErrorProvider = new  System.Windows.Forms.ErrorProvider();
            ageErrorProvider.SetIconAlignment (this.ageUpDownPicker, ErrorIconAlignment.MiddleRight);
            ageErrorProvider.SetIconPadding (this.ageUpDownPicker, 2);
            ageErrorProvider.BlinkStyle = System.Windows.Forms.ErrorBlinkStyle.BlinkIfDifferentError;

            favoriteColorErrorProvider = new  System.Windows.Forms.ErrorProvider();
            favoriteColorErrorProvider.SetIconAlignment (this.favoriteColorComboBox, ErrorIconAlignment.MiddleRight);
            favoriteColorErrorProvider.SetIconPadding (this.favoriteColorComboBox, 2);
            favoriteColorErrorProvider.BlinkRate = 1000;
            favoriteColorErrorProvider.BlinkStyle = System.Windows.Forms.ErrorBlinkStyle.NeverBlink;
        }
    
        private void nameTextBox1_Validated(object sender, System.EventArgs e)
        {
            if(IsNameValid())
            {
                // Clear the error, if any, in the error provider.
                nameErrorProvider.SetError(this.nameTextBox1, String.Empty);
            }
            else
            {
                // Set the error if the name is not valid.
                nameErrorProvider.SetError(this.nameTextBox1, "Name is required.");
            }
        }

        private void ageUpDownPicker_Validated(object sender, System.EventArgs e)
        {
            if (IsAgeTooYoung())
            {
                // Set the error if the age is too young.
                ageErrorProvider.SetError(this.ageUpDownPicker, "Age not old enough");
            }
            else if (IsAgeTooOld())
            {
                // Set the error if the age is too old.
                ageErrorProvider.SetError(this.ageUpDownPicker, "Age is too old");
            }
            else 
            {
                // Clear the error, if any, in the error provider.
                ageErrorProvider.SetError(this.ageUpDownPicker, String.Empty);
            }
        }

        private void favoriteColorComboBox_Validated(object sender, System.EventArgs e) 
        {
            if (!IsColorValid())
            {
                // Set the error if the favorite color is not valid.
                favoriteColorErrorProvider.SetError(this.favoriteColorComboBox, "Must select a color.");
            }
            else
            {
                // Clear the error, if any, in the error provider.
                favoriteColorErrorProvider.SetError(this.favoriteColorComboBox, String.Empty);
            }
        }

        // Functions to verify data.
        private bool IsNameValid() 
        {
            // Determine whether the text box contains a zero-length string.
            return (nameTextBox1.Text.Length > 0);
        }

        private bool IsAgeTooYoung() 
        {
            // Determine whether the age value is less than three.
            return (ageUpDownPicker.Value < 3);
        }

        private bool IsAgeTooOld() 
        {
            // Determine whether the age value is greater than five.
            return (ageUpDownPicker.Value > 5 );
        }

        private bool IsColorValid() 
        {
            // Determine whether the favorite color has a valid value.
            return ((favoriteColorComboBox.SelectedItem != null) &&
                (!favoriteColorComboBox.SelectedItem.ToString().Equals("None")));
        }
    }
}
Imports System
Imports System.Drawing
Imports System.Windows.Forms

Namespace ErrorProvider

    Public NotInheritable Class Form1
        Inherits System.Windows.Forms.Form
    
        Private label1 As System.Windows.Forms.Label
        Private label2 As System.Windows.Forms.Label
        Private label3 As System.Windows.Forms.Label      
        Private label4 As System.Windows.Forms.Label
        Private label5 As System.Windows.Forms.Label
        Private label6 As System.Windows.Forms.Label
        Friend WithEvents favoriteColorComboBox As System.Windows.Forms.ComboBox 
        Friend WithEvents nameTextBox1 As System.Windows.Forms.TextBox 
        Friend WithEvents ageUpDownPicker As System.Windows.Forms.NumericUpDown      
        Private ageErrorProvider As System.Windows.Forms.ErrorProvider 
        Private nameErrorProvider As System.Windows.Forms.ErrorProvider 
        Private favoriteColorErrorProvider As System.Windows.Forms.ErrorProvider
        
        <System.STAThread()>  _
        Public Shared Sub Main()
            System.Windows.Forms.Application.Run(New Form1())
        End Sub 'Main

        Public Sub New()
            
            Me.nameTextBox1 = New System.Windows.Forms.TextBox()
            Me.label1 = New System.Windows.Forms.Label()
            Me.label2 = New System.Windows.Forms.Label()
            Me.ageUpDownPicker = New System.Windows.Forms.NumericUpDown()
            Me.favoriteColorComboBox = New System.Windows.Forms.ComboBox()
            Me.label3 = New System.Windows.Forms.Label()
            Me.label4 = New System.Windows.Forms.Label()
            Me.label5 = New System.Windows.Forms.Label()
            Me.label6 = New System.Windows.Forms.Label()

            ' Name Label
            Me.label1.Location = New System.Drawing.Point(56, 32)
            Me.label1.Size = New System.Drawing.Size(40, 23)
            Me.label1.Text = "Name:"

            ' Age Label
            Me.label2.Location = New System.Drawing.Point(40, 64)
            Me.label2.Size = New System.Drawing.Size(56, 23)
            Me.label2.Text = "Age (3-5)"

            ' Favorite Color Label
            Me.label3.Location = New System.Drawing.Point(24, 96)
            Me.label3.Size = New System.Drawing.Size(80, 24)
            Me.label3.Text = "Favorite color"

            ' ErrorBlinkStyle.AlwaysBlink Label
            Me.label4.Location = New System.Drawing.Point(264, 32)
            Me.label4.Size = New System.Drawing.Size(160, 23)
            Me.label4.Text = "ErrorBlinkStyle.AlwaysBlink"

            ' ErrorBlinkStyle.BlinkIfDifferentError Label
            Me.label5.Location = New System.Drawing.Point(264, 64)
            Me.label5.Size = New System.Drawing.Size(200, 23)
            Me.label5.Text = "ErrorBlinkStyle.BlinkIfDifferentError"

            ' ErrorBlinkStyle.NeverBlink Label
            Me.label6.Location = New System.Drawing.Point(264, 96)
            Me.label6.Size = New System.Drawing.Size(200, 23)
            Me.label6.Text = "ErrorBlinkStyle.NeverBlink"

            ' Name TextBox
            Me.nameTextBox1.Location = New System.Drawing.Point(112, 32)
            Me.nameTextBox1.Size = New System.Drawing.Size(120, 20)
            Me.nameTextBox1.TabIndex = 0

            ' Age NumericUpDown
            Me.ageUpDownPicker.Location = New System.Drawing.Point(112, 64)
            Me.ageUpDownPicker.Maximum = New System.Decimal(New Integer() {150, 0, 0, 0})
            Me.ageUpDownPicker.TabIndex = 4

            ' Favorite Color ComboBox
            Me.favoriteColorComboBox.Items.AddRange(New Object() {"None", "Red", "Yellow", _
                                                                                    "Green", "Blue", "Purple"})
            Me.favoriteColorComboBox.Location = New System.Drawing.Point(112, 96)
            Me.favoriteColorComboBox.Size = New System.Drawing.Size(120, 21)
            Me.favoriteColorComboBox.TabIndex = 5

            ' Set up how the form should be displayed and add the controls to the form.
            Me.ClientSize = New System.Drawing.Size(464, 150)
            Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.label6, Me.label5, Me.label4, _
                                          Me.label3, Me.favoriteColorComboBox, Me.ageUpDownPicker, Me.label2, _
                                          Me.label1, Me.nameTextBox1})

            Me.Text = "Error Provider Example"

            ' Create and set the ErrorProvider for each data entry control.
     
            nameErrorProvider = New System.Windows.Forms.ErrorProvider()
            nameErrorProvider.SetIconAlignment(Me.nameTextBox1, ErrorIconAlignment.MiddleRight)
            nameErrorProvider.SetIconPadding(Me.nameTextBox1, 2)
            nameErrorProvider.BlinkRate = 1000
            nameErrorProvider.BlinkStyle = System.Windows.Forms.ErrorBlinkStyle.AlwaysBlink
            
            ageErrorProvider = New System.Windows.Forms.ErrorProvider()
            ageErrorProvider.SetIconAlignment(Me.ageUpDownPicker, ErrorIconAlignment.MiddleRight)
            ageErrorProvider.SetIconPadding(Me.ageUpDownPicker, 2)
            ageErrorProvider.BlinkStyle = System.Windows.Forms.ErrorBlinkStyle.BlinkIfDifferentError
            
            favoriteColorErrorProvider = New System.Windows.Forms.ErrorProvider()
            favoriteColorErrorProvider.SetIconAlignment(Me.favoriteColorComboBox, ErrorIconAlignment.MiddleRight)
            favoriteColorErrorProvider.SetIconPadding(Me.favoriteColorComboBox, 2)
            favoriteColorErrorProvider.BlinkRate = 1000
            favoriteColorErrorProvider.BlinkStyle = System.Windows.Forms.ErrorBlinkStyle.NeverBlink
        End Sub 'New
 
        Private Sub nameTextBox1_Validated(sender As Object, e As System.EventArgs) Handles nameTextBox1.Validated
            If IsNameValid() Then
                ' Clear the error, if any, in the error provider.
                nameErrorProvider.SetError(Me.nameTextBox1, String.Empty)
            Else
                ' Set the error if the name is not valid.
                nameErrorProvider.SetError(Me.nameTextBox1, "Name is required.")
            End If 
        End Sub 
              
        Private Sub ageUpDownPicker_Validated(sender As Object, e As System.EventArgs) Handles ageUpDownPicker.Validated
            If IsAgeTooYoung() Then
                ' Set the error if the age is too young.
                ageErrorProvider.SetError(Me.ageUpDownPicker, "Age not old enough")
            ElseIf IsAgeTooOld() Then
                ' Set the error if the age is too old.
                ageErrorProvider.SetError(Me.ageUpDownPicker, "Age is too old")
            Else
                ' Clear the error, if any, in the error provider.
                ageErrorProvider.SetError(Me.ageUpDownPicker, String.Empty)
            End If
        End Sub
         
        Private Sub favoriteColorComboBox_Validated(sender As Object, e As System.EventArgs) Handles favoriteColorComboBox.Validated
            If Not IsColorValid() Then
                ' Set the error if the favorite color is not valid.
                favoriteColorErrorProvider.SetError(Me.favoriteColorComboBox, "Must select a color.")            
            Else
                ' Clear the error, if any, in the error provider.
                favoriteColorErrorProvider.SetError(Me.favoriteColorComboBox, String.Empty)
            End If
        End Sub 

        ' Functions to verify data.
        Private Function IsNameValid() As Boolean
            ' Determine whether the text box contains a zero-length string.
            Return nameTextBox1.Text.Length > 0
        End Function 

        Private Function IsAgeTooYoung() As Boolean
            ' Determine whether the age value is less than three.
            Return ageUpDownPicker.Value < 3
        End Function 
        
        
        Private Function IsAgeTooOld() As Boolean
            ' Determine whether the age value is greater than five.
            Return ageUpDownPicker.Value > 5
        End Function 
                
        Private Function IsColorValid() As Boolean
            ' Determine whether the favorite color has a valid value.
            If (favoriteColorComboBox.SelectedItem IsNot Nothing) Then
                    If Not(favoriteColorComboBox.SelectedItem.ToString().Equals("None")) Then
                        Return true 
                    End If
            End If
            Return false
        End Function 

    End Class 'Form1
End Namespace 'ErrorProvider 

Remarks

If the length of value is greater than zero, then the error icon is displayed, and the ToolTip for the error icon is the error description text. If the length is zero or value is null, the error icon is hidden.

Applies to

See Also