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ErrorProvider Class

Provides a user interface for indicating that a control on a form has an error associated with it.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

[ComplexBindingPropertiesAttribute("DataSource", "DataMember")]
public class ErrorProvider : Component, 
	IExtenderProvider, ISupportInitialize

ErrorProvider presents a simple mechanism for indicating to the end user that a control on a form has an error associated with it. If an error description string is specified for the control, an icon appears next to the control. The icon flashes in the manner specified by BlinkStyle, at the rate specified by BlinkRate. When the mouse hovers over the icon, a ToolTip appears showing the error description string.

Typically, you use ErrorProvider in association with data-bound controls. When using ErrorProvider with data-bound controls, you must specify the ContainerControl, either in the constructor or by setting the ContainerControl property.

NoteNote:

The ErrorProvider component does not provide built-in support for accessibility clients. To make your application accessible when using this component, you must provide an additional, accessible feedback mechanism.

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;
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, "");
            }
            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, "");
            }
        }

        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, "");
            }
        }

        // 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")));
        }
    }
}

The following code example shows how to use the ErrorProvider with a DataSource and DataMember to indicate a data error to the user.

private void InitializeComponent()
 {
     // Standard control setup. 
     //.... 
     // You set the DataSource to a data set, and the DataMember to a table.
     errorProvider1.DataSource = dataSet1 ;
     errorProvider1.DataMember = dataTable1.TableName ;
     errorProvider1.ContainerControl = this ;
     errorProvider1.BlinkRate = 200 ;
     //... 
     // Since the ErrorProvider control does not have a visible component, 
     // it does not need to be added to the form. 
 }

 private void buttonSave_Click(object sender, System.EventArgs e)
 {
     // Checks for a bad post code.
     DataTable CustomersTable;
     CustomersTable = dataSet1.Tables["Customers"];
     foreach (DataRow row in (CustomersTable.Rows)) 
	 {
         if (Convert.ToBoolean(row["PostalCodeIsNull"])) 
         {
             row.RowError="The Customer details contain errors";
             row.SetColumnError("PostalCode", "Postal Code required");
         } 
     } 
 }

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
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