ErrorProvider.SetError(Control, String) 方法
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
設定指定控制項的錯誤描述字串。
public:
void SetError(System::Windows::Forms::Control ^ control, System::String ^ value);public void SetError (System.Windows.Forms.Control control, string value);public void SetError (System.Windows.Forms.Control control, string? value);member this.SetError : System.Windows.Forms.Control * string -> unitPublic Sub SetError (control As Control, value As String)參數
- control
- Control
要為其設定錯誤描述字串的控制項。
例外狀況
control 為 null。
範例
下列程式碼範例示範如何使用 ErrorProvider 類別來通知使用者資料輸入錯誤。 此範例會建立 ， Form 其中包含控制項、 NumericUpDown 控制項和 ComboBox 控制項、每個驗證其內容，以及每個控制項的 ErrorProviderTextBox 。 此範例會使用 BlinkRate 和 BlinkStyle 屬性和 SetIconAlignment 和 SetIconPadding 方法來設定錯誤圖示選項。 方法 SetError 會在控制項的 Validated 事件期間使用或不含適當的錯誤文字呼叫，視控制項中的內容而定。
#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.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
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
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
End Namespace 'ErrorProvider
備註
如果 的 value 長度大於零，則會顯示錯誤圖示，而錯誤圖示的工具提示則是錯誤描述文字。 如果長度為零或 value 為 null ，則會隱藏錯誤圖示。
