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HelpProvider.GetHelpString(Control) Method

  • Reference

Definition

Namespace:
System.Windows.Forms
Assembly:
System.Windows.Forms.dll

Returns the contents of the pop-up Help window for the specified control.

public:
 virtual System::String ^ GetHelpString(System::Windows::Forms::Control ^ ctl);
public virtual string GetHelpString (System.Windows.Forms.Control ctl);
public virtual string? GetHelpString (System.Windows.Forms.Control ctl);
abstract member GetHelpString : System.Windows.Forms.Control -> string
override this.GetHelpString : System.Windows.Forms.Control -> string
Public Overridable Function GetHelpString (ctl As Control) As String

Parameters

ctl
Control

A Control from which to retrieve the Help string.

Returns

String

The Help string associated with this control. The default is null.

Examples

The following code example shows how to use the KeyPressEventHandler and KeyEventHandler classes to filter input. It also demonstrates the GetHelpString method. This is a complete example; it is ready to run once you add it to your project.

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

using namespace System::Drawing;
using namespace System::Windows::Forms;
using namespace System;
using namespace Microsoft::VisualBasic;
public ref class Form1: public System::Windows::Forms::Form
{
public:
   Form1()
      : Form()
   {
      InitializeComponent();
      AddHandlers();
      InitializeFormHelp();
   }


public private:
   System::Windows::Forms::Label ^ Label1;
   System::Windows::Forms::Label ^ Label2;
   System::Windows::Forms::Label ^ Label3;
   System::Windows::Forms::TextBox^ withdrawal;
   System::Windows::Forms::TextBox^ deposit;
   System::Windows::Forms::ErrorProvider^ ErrorProvider1;
   System::Windows::Forms::Label ^ balance;
   System::Windows::Forms::HelpProvider^ HelpProvider1;

private:

   [System::Diagnostics::DebuggerStepThrough]
   void InitializeComponent()
   {
      this->withdrawal = gcnew System::Windows::Forms::TextBox;
      this->deposit = gcnew System::Windows::Forms::TextBox;
      this->Label1 = gcnew System::Windows::Forms::Label;
      this->Label2 = gcnew System::Windows::Forms::Label;
      this->Label3 = gcnew System::Windows::Forms::Label;
      this->ErrorProvider1 = gcnew System::Windows::Forms::ErrorProvider;
      this->balance = gcnew System::Windows::Forms::Label;
      this->HelpProvider1 = gcnew System::Windows::Forms::HelpProvider;
      this->SuspendLayout();
      this->withdrawal->Location = System::Drawing::Point( 32, 200 );
      this->withdrawal->Name = "withdrawal";
      this->withdrawal->Size = System::Drawing::Size( 88, 20 );
      this->withdrawal->TabIndex = 0;
      this->withdrawal->Text = "";
      this->deposit->Location = System::Drawing::Point( 168, 200 );
      this->deposit->Name = "deposit";
      this->deposit->TabIndex = 1;
      this->deposit->Text = "";
      this->Label1->Location = System::Drawing::Point( 56, 88 );
      this->Label1->Name = "Label1";
      this->Label1->Size = System::Drawing::Size( 96, 24 );
      this->Label1->TabIndex = 2;
      this->Label1->Text = "Account Balance:";
      this->Label2->Location = System::Drawing::Point( 168, 168 );
      this->Label2->Name = "Label2";
      this->Label2->Size = System::Drawing::Size( 96, 24 );
      this->Label2->TabIndex = 4;
      this->Label2->Text = "Deposit:";
      this->Label3->Location = System::Drawing::Point( 32, 168 );
      this->Label3->Name = "Label3";
      this->Label3->Size = System::Drawing::Size( 96, 24 );
      this->Label3->TabIndex = 5;
      this->Label3->Text = "Withdrawal:";
      this->ErrorProvider1->ContainerControl = this;
      this->balance->BorderStyle = System::Windows::Forms::BorderStyle::Fixed3D;
      this->balance->Location = System::Drawing::Point( 152, 88 );
      this->balance->Name = "balance";
      this->balance->TabIndex = 6;
      this->balance->Text = "345.65";
      this->balance->TextAlign = System::Drawing::ContentAlignment::MiddleLeft;
      this->ClientSize = System::Drawing::Size( 292, 266 );
      this->Controls->Add( this->balance );
      this->Controls->Add( this->Label3 );
      this->Controls->Add( this->Label2 );
      this->Controls->Add( this->Label1 );
      this->Controls->Add( this->deposit );
      this->Controls->Add( this->withdrawal );
      this->Name = "Form1";
      this->Text = "Form1";
      this->ResumeLayout( false );
   }

   void AddHandlers()
   {
      
      // Add the event-handler delegates to handled the KeyDown
      // events.
      deposit->KeyDown += gcnew KeyEventHandler( this, &Form1::ProcessEntry );
      withdrawal->KeyDown += gcnew KeyEventHandler( this, &Form1::ProcessEntry );
      
      // Add the event-handler delegates to handled the KeyPress 
      // events.
      deposit->KeyPress += gcnew KeyPressEventHandler( this, &Form1::CheckForDigits );
      withdrawal->KeyPress += gcnew KeyPressEventHandler( this, &Form1::CheckForDigits );
   }


   void InitializeFormHelp()
   {
      
      // Set the form's border to the FixedDialog style.
      this->FormBorderStyle = ::FormBorderStyle::FixedDialog;
      
      // Remove the Maximize and Minimize buttons from the form.
      this->MaximizeBox = false;
      this->MinimizeBox = false;
      
      // Add the Help button to the form.
      this->HelpButton = true;
      
      // Set the Help string for the deposit textBox.
      HelpProvider1->SetHelpString( deposit, "Enter an amount in the format xxx.xx"
      "and press Enter to deposit." );
      
      // Set the Help string for the withdrawal textBox.
      HelpProvider1->SetHelpString( withdrawal, "Enter an amount in the format xxx.xx"
      "and press Enter to withdraw." );
   }




   void ProcessEntry( Object^ sender, KeyEventArgs^ e )
   {
      
      // Cast the sender back to a TextBox.
      Control^ textBoxSender = dynamic_cast<TextBox^>(sender);
      
      // Set the error description to an empty string ().
      ErrorProvider1->SetError( textBoxSender, "" );
      
      // Declare the variable to hold the new balance.
      double newBalance = 0;
      
      // Wrap the code in a Try/Catch block to catch 
      // errors that can occur when converting the string 
      // to a double.
      try
      {
         if ( e->KeyCode == Keys::Enter )
         {
            if ( textBoxSender->Name->Equals( "withdrawal" ) )
            {
               newBalance = Double::Parse( balance->Text ) - Double::Parse( withdrawal->Text );
               withdrawal->Text = "";
            }
            else
            if ( textBoxSender->Name->Equals( "deposit" ) )
            {
               newBalance = Double::Parse( balance->Text ) + Double::Parse( deposit->Text );
               deposit->Text = "";
            }
            
            // Check the value of new balance and set the
            // Forecolor property accordingly.
            if ( newBalance < 0 )
            {
               balance->ForeColor = Color::Red;
            }
            else
            {
               balance->ForeColor = Color::Black;
            }
            
            // Set the text of the balance text box
            // to the newBalance value.
            balance->Text = newBalance.ToString();
         }
      }
      catch ( FormatException^ ) 
      {
         
         // If a FormatException is thrown, set the
         // error string to the HelpString message for 
         // the control.
         ErrorProvider1->SetError( textBoxSender, HelpProvider1->GetHelpString( textBoxSender ) );
      }

   }

   void CheckForDigits( Object^ /*sender*/, KeyPressEventArgs^ e )
   {
      
      // If the character is not a digit, period, or backspace then
      // ignore it by setting the KeyPressEventArgs.Handled
      // property to true.
      if (  !(Char::IsDigit( e->KeyChar ) || e->KeyChar == '.' || e->KeyChar == (char)(Keys::Back)) )
      {
         e->Handled = true;
      }
   }

};

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

   
using System.Drawing;
using System.Windows.Forms;
using System;
using Microsoft.VisualBasic;

public class Form1:
    System.Windows.Forms.Form

{

    public Form1() : base()
    {        

        InitializeComponent();
        AddHandlers();
        InitializeFormHelp();
    }

    internal System.Windows.Forms.Label Label1;
    internal System.Windows.Forms.Label Label2;
    internal System.Windows.Forms.Label Label3;
    internal System.Windows.Forms.TextBox withdrawal;
    internal System.Windows.Forms.TextBox deposit;
    internal System.Windows.Forms.ErrorProvider ErrorProvider1;
    internal System.Windows.Forms.Label balance;
    internal System.Windows.Forms.HelpProvider HelpProvider1;
    
[System.Diagnostics.DebuggerStepThrough]
    private void InitializeComponent()
    {
        this.withdrawal = new System.Windows.Forms.TextBox();
        this.deposit = new System.Windows.Forms.TextBox();
        this.Label1 = new System.Windows.Forms.Label();
        this.Label2 = new System.Windows.Forms.Label();
        this.Label3 = new System.Windows.Forms.Label();
        this.ErrorProvider1 = new 		System.Windows.Forms.ErrorProvider();
        this.balance = new System.Windows.Forms.Label();
        this.HelpProvider1 = new 		System.Windows.Forms.HelpProvider();
        this.SuspendLayout();
        
        this.withdrawal.Location = new System.Drawing.Point(32, 200);
        this.withdrawal.Name = "withdrawal";
        this.withdrawal.Size = new System.Drawing.Size(88, 20);
        this.withdrawal.TabIndex = 0;
        this.withdrawal.Text = "";
        
        this.deposit.Location = new System.Drawing.Point(168, 200);
        this.deposit.Name = "deposit";
        this.deposit.TabIndex = 1;
        this.deposit.Text = "";
        
        this.Label1.Location = new System.Drawing.Point(56, 88);
        this.Label1.Name = "Label1";
        this.Label1.Size = new System.Drawing.Size(96, 24);
        this.Label1.TabIndex = 2;
        this.Label1.Text = "Account Balance:";
        
        this.Label2.Location = new System.Drawing.Point(168, 168);
        this.Label2.Name = "Label2";
        this.Label2.Size = new System.Drawing.Size(96, 24);
        this.Label2.TabIndex = 4;
        this.Label2.Text = "Deposit:";
        
        this.Label3.Location = new System.Drawing.Point(32, 168);
        this.Label3.Name = "Label3";
        this.Label3.Size = new System.Drawing.Size(96, 24);
        this.Label3.TabIndex = 5;
        this.Label3.Text = "Withdrawal:";
        
        this.ErrorProvider1.ContainerControl = this;
        
        this.balance.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
        this.balance.Location = new System.Drawing.Point(152, 88);
        this.balance.Name = "balance";
        this.balance.TabIndex = 6;
        this.balance.Text = "345.65";
        this.balance.TextAlign = System.Drawing.ContentAlignment.MiddleLeft;
        
        this.ClientSize = new System.Drawing.Size(292, 266);
        this.Controls.Add(this.balance);
        this.Controls.Add(this.Label3);
        this.Controls.Add(this.Label2);
        this.Controls.Add(this.Label1);
        this.Controls.Add(this.deposit);
        this.Controls.Add(this.withdrawal);
        this.Name = "Form1";
        this.Text = "Form1";
        this.ResumeLayout(false);
    }

    private void AddHandlers()
    {
        // Add the event-handler delegates to handled the KeyDown
        // events.
        deposit.KeyDown +=new KeyEventHandler(ProcessEntry);  
        withdrawal.KeyDown += new KeyEventHandler(ProcessEntry);

        // Add the event-handler delegates to handled the KeyPress 
        // events.
        deposit.KeyPress += new KeyPressEventHandler(CheckForDigits);
        withdrawal.KeyPress += 
            new KeyPressEventHandler(CheckForDigits);
    }

    private void InitializeFormHelp()
    {

        // Set the form's border to the FixedDialog style.
        this.FormBorderStyle = FormBorderStyle.FixedDialog;

        // Remove the Maximize and Minimize buttons from the form.
        this.MaximizeBox = false;
        this.MinimizeBox = false;

        // Add the Help button to the form.
        this.HelpButton = true;

        // Set the Help string for the deposit textBox.
        HelpProvider1.SetHelpString(deposit, 
            "Enter an amount in the format xxx.xx" +
            "and press Enter to deposit.");

        // Set the Help string for the withdrawal textBox.
        HelpProvider1.SetHelpString(withdrawal, 
            "Enter an amount in the format xxx.xx" +
            "and press Enter to withdraw.");
    }

    private void ProcessEntry(object sender, KeyEventArgs e)
    {

        // Cast the sender back to a TextBox.
        Control textBoxSender = (TextBox) sender;

        // Set the error description to an empty string ().
        ErrorProvider1.SetError(textBoxSender, "");

        // Declare the variable to hold the new balance.
        double newBalance = 0;

        // Wrap the code in a Try/Catch block to catch 
        // errors that can occur when converting the string 
        // to a double.

        try
        {
            if (e.KeyCode==Keys.Enter)

                // Switch on the text box that received
                // the KeyPress event. Convert the text to type double,
                // and compute the new balance.
            {
                switch(textBoxSender.Name)
                {
                    case "withdrawal":
                        newBalance = Double.Parse(balance.Text) 
                            - Double.Parse(withdrawal.Text);
                        withdrawal.Text = "";
                        break;
                    case "deposit":
                        newBalance = Double.Parse(balance.Text) 
                            + Double.Parse(deposit.Text);
                        deposit.Text = "";
                        break;
                }

                // Check the value of new balance and set the
                // Forecolor property accordingly.
                if (newBalance < 0)
                {
                    balance.ForeColor = Color.Red;
                }
                else
                {
                    balance.ForeColor = Color.Black;
                }

                // Set the text of the balance text box
                // to the newBalance value.
                balance.Text = newBalance.ToString();
            }
        }
        catch(FormatException)
        {

            // If a FormatException is thrown, set the
            // error string to the HelpString message for 
            // the control.
            ErrorProvider1.SetError(textBoxSender, 
                HelpProvider1.GetHelpString(textBoxSender));
        }
    }

    private void CheckForDigits(object sender, KeyPressEventArgs e)
    {

        // If the character is not a digit, period, or backspace then
        // ignore it by setting the KeyPressEventArgs.Handled
        // property to true.
        if (!(Char.IsDigit(e.KeyChar) || e.KeyChar == '.' || 
            e.KeyChar == (char)(Keys.Back)))
        {
            e.Handled = true;
        }
    }

    public static void Main()
    {
        Application.Run(new Form1());
    }
}

Imports System.Drawing
Imports System.Windows.Forms

Public Class Form1
    Inherits System.Windows.Forms.Form

    Public Sub New()
        MyBase.New()

        InitializeComponent()
        AddHandlers()
        InitializeFormHelp()

    End Sub

    
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents Label2 As System.Windows.Forms.Label
    Friend WithEvents Label3 As System.Windows.Forms.Label
    Friend WithEvents withdrawal As System.Windows.Forms.TextBox
    Friend WithEvents deposit As System.Windows.Forms.TextBox
    Friend WithEvents ErrorProvider1 As System.Windows.Forms.ErrorProvider
    Friend WithEvents balance As System.Windows.Forms.Label
    Friend WithEvents HelpProvider1 As System.Windows.Forms.HelpProvider

   <System.Diagnostics.DebuggerStepThrough()> Private Sub     InitializeComponent()
        Me.withdrawal = New System.Windows.Forms.TextBox
        Me.deposit = New System.Windows.Forms.TextBox
        Me.Label1 = New System.Windows.Forms.Label
        Me.Label2 = New System.Windows.Forms.Label
        Me.Label3 = New System.Windows.Forms.Label
        Me.ErrorProvider1 = New System.Windows.Forms.ErrorProvider
        Me.balance = New System.Windows.Forms.Label
        Me.HelpProvider1 = New System.Windows.Forms.HelpProvider
        Me.SuspendLayout()
        
        Me.withdrawal.Location = New System.Drawing.Point(32, 200)
        Me.withdrawal.Name = "withdrawal"
        Me.withdrawal.Size = New System.Drawing.Size(88, 20)
        Me.withdrawal.TabIndex = 0
        Me.withdrawal.Text = ""
       
        Me.deposit.Location = New System.Drawing.Point(168, 200)
        Me.deposit.Name = "deposit"
        Me.deposit.TabIndex = 1
        Me.deposit.Text = ""
       
        Me.Label1.Location = New System.Drawing.Point(56, 88)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(96, 24)
        Me.Label1.TabIndex = 2
        Me.Label1.Text = "Account Balance:"
       
        Me.Label2.Location = New System.Drawing.Point(168, 168)
        Me.Label2.Name = "Label2"
        Me.Label2.Size = New System.Drawing.Size(96, 24)
        Me.Label2.TabIndex = 4
        Me.Label2.Text = "Deposit:"
        
        Me.Label3.Location = New System.Drawing.Point(32, 168)
        Me.Label3.Name = "Label3"
        Me.Label3.Size = New System.Drawing.Size(96, 24)
        Me.Label3.TabIndex = 5
        Me.Label3.Text = "Withdrawal:"
        
        Me.ErrorProvider1.ContainerControl = Me
        
        Me.balance.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D
        Me.balance.Location = New System.Drawing.Point(152, 88)
        Me.balance.Name = "balance"
        Me.balance.TabIndex = 6
        Me.balance.Text = "345.65"
        Me.balance.TextAlign = System.Drawing.ContentAlignment.MiddleLeft
        
        Me.ClientSize = New System.Drawing.Size(292, 266)
        Me.Controls.Add(Me.balance)
        Me.Controls.Add(Me.Label3)
        Me.Controls.Add(Me.Label2)
        Me.Controls.Add(Me.Label1)
        Me.Controls.Add(Me.deposit)
        Me.Controls.Add(Me.withdrawal)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub
 
   
    
    Private Sub AddHandlers()

        'Add the event-handler delegates to handle the KeyDown events.
        AddHandler deposit.KeyDown, _
            New KeyEventHandler(AddressOf ProcessEntry)
        AddHandler withdrawal.KeyDown, _
            New KeyEventHandler(AddressOf ProcessEntry)

        'Add the event-handler delegates to handled the KeyPress events.
        AddHandler deposit.KeyPress, _
            New KeyPressEventHandler(AddressOf CheckForDigits)
        AddHandler withdrawal.KeyPress, _
            New KeyPressEventHandler(AddressOf CheckForDigits)

    End Sub
    Private Sub InitializeFormHelp()

        ' Set the form's border to the FixedDialog style.
        Me.FormBorderStyle = FormBorderStyle.FixedDialog

        ' Remove the Maximize and Minimize buttons from the form.
        Me.MaximizeBox = False
        Me.MinimizeBox = False

        ' Add the Help button to the form.
        Me.HelpButton = True

        ' Set the Help string for the deposit textBox.
        HelpProvider1.SetHelpString(deposit, _
            "Enter an amount in the format xxx.xx" _
                & "and press Enter to deposit.")

        ' Set the Help string for the withdrawal textBox.
        HelpProvider1.SetHelpString(withdrawal, _
            "Enter an amount in the format xxx.xx" _
            & "and press Enter to withdraw.")

    End Sub

    Private Sub ProcessEntry(ByVal sender As Object, _
        ByVal e As KeyEventArgs)

        ' Cast the sender back to a TextBox.
        Dim textBoxSender As Control = CType(sender, TextBox)

        ' Set the error description to an empty string ().
        ErrorProvider1.SetError(textBoxSender, "")

        ' Declare the variable to hold the new balance.
        Dim newBalance As Double

        ' Wrap the code in a Try/Catch block to catch 
        ' errors that can occur when converting the string 
        ' to a double.

        Try
            If (e.KeyCode = Keys.Enter) Then

                ' Switch on the text box that received
                ' the KeyPress event. Convert the text to type double,
                ' and compute the new balance.
                Select Case textBoxSender.Name
                    Case "withdrawal"
                        newBalance = Double.Parse(balance.Text) _
                            - Double.Parse(withdrawal.Text)
                        withdrawal.Text = ""
                    Case "deposit"
                        newBalance = Double.Parse(balance.Text) _
                            + Double.Parse(deposit.Text)
                        deposit.Text = ""
                End Select

                ' Check the value of new balance and set the
                ' Forecolor property accordingly.
                If (newBalance < 0) Then
                    balance.ForeColor = Color.Red
                Else
                    balance.ForeColor = Color.Black
                End If

                ' Set the text of the balance text box
                ' to the newBalance value.
                balance.Text = newBalance.ToString
            End If

        Catch ex As FormatException

            ' If a FormatException is thrown, set the
            ' error string to the HelpString message for 
            ' the control.
            ErrorProvider1.SetError(textBoxSender, _
                HelpProvider1.GetHelpString(textBoxSender))
        End Try
    End Sub


    Private Sub CheckForDigits(ByVal sender As Object, ByVal e _
        As KeyPressEventArgs)

        ' If the character is not a digit, period, or backspace then
        ' ignore it by setting the KeyPressEventArgs.Handled
        ' property to true.
        If Not (Char.IsDigit(e.KeyChar) _
            Or e.KeyChar = "." Or e.KeyChar = ChrW(Keys.Back)) Then
            e.Handled = True
        End If
    End Sub
   

    Public Shared Sub Main()
        Application.Run(New Form1)
    End Sub

End Class

Remarks

To display this Help string at run time, the user presses the F1 key while the specified control has the input focus.

Applies to

See also