ComboBox.MaxDropDownItems Свойство
Определение
Важно!
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Возвращает или задает максимальное число элементов, отображаемых в раскрывающемся списке элемента управления ComboBox.
public:
property int MaxDropDownItems { int get(); void set(int value); };public int MaxDropDownItems { get; set; }member this.MaxDropDownItems : int with get, setPublic Property MaxDropDownItems As IntegerЗначение свойства
Максимальное число элементов в раскрывающейся части поля со списком. Минимальным значением этого свойства является 1, максимальным — 100.
Исключения
Для максимального числа задается значение менее единицы или более 100.
Примеры
В следующем примере кода показано, как инициализировать ComboBox элемент управления, задав MaxDropDownItems свойства и и DropDownStyle используя FindStringExact методы для поиска в ComboBox. Здесь также показана SelectedIndexChanged обработка события.
#using <System.Drawing.dll>
#using <System.dll>
#using <System.Windows.Forms.dll>
using namespace System::Windows::Forms;
using namespace System;
public ref class Form1: public System::Windows::Forms::Form
{
public:
Form1() : Form()
{
InitializeComboBox();
InitializeTextBox();
this->Label1 = gcnew System::Windows::Forms::Label;
this->SuspendLayout();
this->Label1->Location = System::Drawing::Point( 8, 24 );
this->Label1->Name = "Label1";
this->Label1->Size = System::Drawing::Size( 120, 32 );
this->Label1->TabIndex = 1;
this->Label1->Text = "Use drop-down to choose a name:";
this->Label1->TextAlign = System::Drawing::ContentAlignment::MiddleRight;
this->ClientSize = System::Drawing::Size( 292, 266 );
this->Controls->Add( this->Label1 );
this->Name = "Form1";
this->Text = "Form1";
this->ResumeLayout( false );
}
internal:
System::Windows::Forms::Label ^ Label1;
// Declare and initialize the text box.
internal:
// This text box text will be update programmatically. The user is not
// allowed to update it, so the ReadOnly property is set to true.
System::Windows::Forms::TextBox^ TextBox1;
private:
void InitializeTextBox()
{
this->TextBox1 = gcnew System::Windows::Forms::TextBox;
this->TextBox1->ScrollBars = ScrollBars::Vertical;
this->TextBox1->Location = System::Drawing::Point( 64, 128 );
this->TextBox1->Multiline = true;
this->TextBox1->Name = "TextBox1";
this->TextBox1->ReadOnly = true;
this->TextBox1->Size = System::Drawing::Size( 184, 120 );
this->TextBox1->TabIndex = 4;
this->TextBox1->Text = "Employee and Number of Awards:";
this->Controls->Add( this->TextBox1 );
}
// Declare comboBox1 as a ComboBox.
internal:
System::Windows::Forms::ComboBox^ ComboBox1;
private:
// This method initializes the combo box, adding a large string array
// but limiting the drop-down size to six rows so the combo box doesn't
// cover other controls when it expands.
void InitializeComboBox()
{
this->ComboBox1 = gcnew System::Windows::Forms::ComboBox;
array<String^>^ employees = {"Hamilton, David","Hensien, Kari",
"Hammond, Maria","Harris, Keith","Henshaw, Jeff D.",
"Hanson, Mark","Harnpadoungsataya, Sariya",
"Harrington, Mark","Harris, Keith","Hartwig, Doris",
"Harui, Roger","Hassall, Mark","Hasselberg, Jonas",
"Harnpadoungsataya, Sariya","Henshaw, Jeff D.",
"Henshaw, Jeff D.","Hensien, Kari","Harris, Keith",
"Henshaw, Jeff D.","Hensien, Kari","Hasselberg, Jonas",
"Harrington, Mark","Hedlund, Magnus","Hay, Jeff",
"Heidepriem, Brandon D."};
ComboBox1->Items->AddRange( employees );
this->ComboBox1->Location = System::Drawing::Point( 136, 32 );
this->ComboBox1->IntegralHeight = false;
this->ComboBox1->MaxDropDownItems = 5;
this->ComboBox1->DropDownStyle = ComboBoxStyle::DropDownList;
this->ComboBox1->Name = "ComboBox1";
this->ComboBox1->Size = System::Drawing::Size( 136, 81 );
this->ComboBox1->TabIndex = 0;
this->Controls->Add( this->ComboBox1 );
// Associate the event-handling method with the
// SelectedIndexChanged event.
this->ComboBox1->SelectedIndexChanged +=
gcnew System::EventHandler( this, &Form1::ComboBox1_SelectedIndexChanged );
}
private:
// This method is called when the user changes his or her selection.
// It searches for all occurrences of the selected employee's
// name in the Items array and adds the employee's name and
// the number of occurrences to TextBox1.Text.
// CAUTION This code exposes a known bug: If the index passed to the
// FindStringExact(searchString, index) method is the last index
// of the array, the code throws an exception.
void ComboBox1_SelectedIndexChanged( Object^ sender,
System::EventArgs^ e )
{
ComboBox^ comboBox = (ComboBox^)(sender);
// Save the selected employee's name, because we will remove
// the employee's name from the list.
String^ selectedEmployee = (String^)(ComboBox1->SelectedItem);
int count = 0;
int resultIndex = -1;
// Call the FindStringExact method to find the first
// occurrence in the list.
resultIndex = ComboBox1->FindStringExact( selectedEmployee );
// Remove the name as it is found, and increment the found count.
// Then call the FindStringExact method again, passing in the
// index of the current found item so the search starts there
// instead of at the beginning of the list.
while ( resultIndex != -1 )
{
ComboBox1->Items->RemoveAt( resultIndex );
count += 1;
resultIndex = ComboBox1->FindStringExact( selectedEmployee,
resultIndex );
}
TextBox1->Text = TextBox1->Text + "\r\n" + selectedEmployee + ": " +
count;
}
};
int main()
{
Application::Run( gcnew Form1 );
}
using System.Windows.Forms;
public class Form1:
System.Windows.Forms.Form
{
public Form1() : base()
{
InitializeComboBox();
InitializeTextBox();
this.Label1 = new System.Windows.Forms.Label();
this.SuspendLayout();
this.Label1.Location = new System.Drawing.Point(8, 24);
this.Label1.Name = "Label1";
this.Label1.Size = new System.Drawing.Size(120, 32);
this.Label1.TabIndex = 1;
this.Label1.Text = "Use drop-down to choose a name:";
this.Label1.TextAlign = System.Drawing.ContentAlignment.MiddleRight;
this.ClientSize = new System.Drawing.Size(292, 266);
this.Controls.Add(this.Label1);
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
}
public static void Main()
{
Application.Run(new Form1());
}
internal System.Windows.Forms.Label Label1;
// Declare and initialize the text box.
// This text box text will be update programmatically. The user is not
// allowed to update it, so the ReadOnly property is set to true.
internal System.Windows.Forms.TextBox TextBox1;
private void InitializeTextBox()
{
this.TextBox1 = new System.Windows.Forms.TextBox();
this.TextBox1.ScrollBars = ScrollBars.Vertical;
this.TextBox1.Location = new System.Drawing.Point(64, 128);
this.TextBox1.Multiline = true;
this.TextBox1.Name = "TextBox1";
this.TextBox1.ReadOnly = true;
this.TextBox1.Size = new System.Drawing.Size(184, 120);
this.TextBox1.TabIndex = 4;
this.TextBox1.Text = "Employee and Number of Awards:";
this.Controls.Add(this.TextBox1);
}
// Declare comboBox1 as a ComboBox.
internal System.Windows.Forms.ComboBox ComboBox1;
// This method initializes the combo box, adding a large string array
// but limiting the drop-down size to six rows so the combo box doesn't
// cover other controls when it expands.
private void InitializeComboBox()
{
this.ComboBox1 = new System.Windows.Forms.ComboBox();
string[] employees = new string[]{"Hamilton, David", "Hensien, Kari",
"Hammond, Maria", "Harris, Keith", "Henshaw, Jeff D.",
"Hanson, Mark", "Harnpadoungsataya, Sariya",
"Harrington, Mark", "Harris, Keith", "Hartwig, Doris",
"Harui, Roger", "Hassall, Mark", "Hasselberg, Jonas",
"Harnpadoungsataya, Sariya", "Henshaw, Jeff D.",
"Henshaw, Jeff D.", "Hensien, Kari", "Harris, Keith",
"Henshaw, Jeff D.", "Hensien, Kari", "Hasselberg, Jonas",
"Harrington, Mark", "Hedlund, Magnus", "Hay, Jeff",
"Heidepriem, Brandon D."};
ComboBox1.Items.AddRange(employees);
this.ComboBox1.Location = new System.Drawing.Point(136, 32);
this.ComboBox1.IntegralHeight = false;
this.ComboBox1.MaxDropDownItems = 5;
this.ComboBox1.DropDownStyle = ComboBoxStyle.DropDownList;
this.ComboBox1.Name = "ComboBox1";
this.ComboBox1.Size = new System.Drawing.Size(136, 81);
this.ComboBox1.TabIndex = 0;
this.Controls.Add(this.ComboBox1);
// Associate the event-handling method with the
// SelectedIndexChanged event.
this.ComboBox1.SelectedIndexChanged +=
new System.EventHandler(ComboBox1_SelectedIndexChanged);
}
// This method is called when the user changes his or her selection.
// It searches for all occurrences of the selected employee's
// name in the Items array and adds the employee's name and
// the number of occurrences to TextBox1.Text.
// CAUTION This code exposes a known bug: If the index passed to the
// FindStringExact(searchString, index) method is the last index
// of the array, the code throws an exception.
private void ComboBox1_SelectedIndexChanged(object sender,
System.EventArgs e)
{
ComboBox comboBox = (ComboBox) sender;
// Save the selected employee's name, because we will remove
// the employee's name from the list.
string selectedEmployee = (string) ComboBox1.SelectedItem;
int count = 0;
int resultIndex = -1;
// Call the FindStringExact method to find the first
// occurrence in the list.
resultIndex = ComboBox1.FindStringExact(selectedEmployee);
// Remove the name as it is found, and increment the found count.
// Then call the FindStringExact method again, passing in the
// index of the current found item so the search starts there
// instead of at the beginning of the list.
while (resultIndex!=-1)
{
ComboBox1.Items.RemoveAt(resultIndex);
count += 1;
resultIndex = ComboBox1.FindStringExact(selectedEmployee,
resultIndex);
}
// Update the text in Textbox1.
TextBox1.Text = TextBox1.Text+ "\r\n" + selectedEmployee + ": "
+ count;
}
}
Imports System.Windows.Forms
Public Class Form1
Inherits System.Windows.Forms.Form
Public Sub New()
MyBase.New()
InitializeComboBox()
InitializeTextBox()
Me.Label1 = New System.Windows.Forms.Label
Me.SuspendLayout()
Me.Label1.Location = New System.Drawing.Point(8, 24)
Me.Label1.Name = "Label1"
Me.Label1.Size = New System.Drawing.Size(120, 32)
Me.Label1.TabIndex = 1
Me.Label1.Text = "Use drop-down to choose a name:"
Me.Label1.TextAlign = System.Drawing.ContentAlignment.MiddleRight
Me.ClientSize = New System.Drawing.Size(292, 266)
Me.Controls.Add(Me.Label1)
Me.Name = "Form1"
Me.Text = "Form1"
Me.ResumeLayout(False)
End Sub
Shared Sub Main()
Application.Run(New Form1)
End Sub
Friend WithEvents Label1 As System.Windows.Forms.Label
' Declare and initialize the text box.
' This text box text will be update programmatically. The user is not
' allowed to update it, so the ReadOnly property is set to true.
Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
Private Sub InitializeTextBox()
Me.TextBox1 = New System.Windows.Forms.TextBox
Me.TextBox1.ScrollBars = ScrollBars.Vertical
Me.TextBox1.Location = New System.Drawing.Point(64, 128)
Me.TextBox1.Multiline = True
Me.TextBox1.Name = "TextBox1"
Me.TextBox1.ReadOnly = True
Me.TextBox1.Size = New System.Drawing.Size(184, 120)
Me.TextBox1.TabIndex = 4
Me.TextBox1.Text = "Employee and Number of Awards:"
Me.Controls.Add(Me.TextBox1)
End Sub
' Declare comboBox1 as a ComboBox.
Friend WithEvents ComboBox1 As System.Windows.Forms.ComboBox
' This method initializes the combo box, adding a large string
' array but limiting the drop-down size to six rows so the combo box
' doesn't cover other controls when it expands.
Private Sub InitializeComboBox()
Me.ComboBox1 = New System.Windows.Forms.ComboBox
Dim employees() As String = New String() {"Hamilton, David", _
"Hensien, Kari", "Hammond, Maria", "Harris, Keith", _
"Henshaw, Jeff D.", "Hanson, Mark", "Harnpadoungsataya, Sariya", _
"Harrington, Mark", "Harris, Keith", "Hartwig, Doris", _
"Harui, Roger", "Hassall, Mark", "Hasselberg, Jonas", _
"Harnpadoungsataya, Sariya", "Henshaw, Jeff D.", "Henshaw, Jeff D.", _
"Hensien, Kari", "Harris, Keith", "Henshaw, Jeff D.", _
"Hensien, Kari", "Hasselberg, Jonas", "Harrington, Mark", _
"Hedlund, Magnus", "Hay, Jeff", "Heidepriem, Brandon D."}
ComboBox1.Items.AddRange(employees)
Me.ComboBox1.Location = New System.Drawing.Point(136, 32)
Me.ComboBox1.IntegralHeight = False
Me.ComboBox1.MaxDropDownItems = 5
Me.ComboBox1.DropDownStyle = ComboBoxStyle.DropDown
Me.ComboBox1.Name = "ComboBox1"
Me.ComboBox1.Size = New System.Drawing.Size(136, 81)
Me.ComboBox1.TabIndex = 0
Me.Controls.Add(Me.ComboBox1)
End Sub
' This method is called when the user changes his or her selection.
' It searches for all occurrences of the selected employee's
' name in the Items array and adds the employee's name and
' the number of occurrences to TextBox1.Text.
' CAUTION This code exposes a known bug: If the index passed to the
' FindStringExact(searchString, index) method is the last index
' of the array, the code throws an exception.
Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
Dim comboBox As comboBox = CType(sender, comboBox)
' Save the selected employee's name, because we will remove
' the employee's name from the list.
Dim selectedEmployee = CType(ComboBox1.SelectedItem, String)
Dim count As Integer = 0
Dim resultIndex As Integer = -1
' Call the FindStringExact method to find the first
' occurrence in the list.
resultIndex = ComboBox1.FindStringExact(ComboBox1.SelectedItem)
' Remove the name as it is found, and increment the found count.
' Then call the FindStringExact method again, passing in the index of the
' current found item so the search starts there instead of
' at the beginning of the list.
While (resultIndex <> -1)
ComboBox1.Items.RemoveAt(resultIndex)
count += 1
resultIndex = ComboBox1.FindStringExact _
(selectedEmployee, resultIndex)
End While
' Update the text in Textbox1.
TextBox1.Text = TextBox1.Text & Microsoft.VisualBasic.vbCrLf _
& selectedEmployee & ": " & count
End Sub
End Class
Применяется к
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