通过

ControlDesigner.ViewControl 属性

  • 参考

定义

命名空间:
System.Web.UI.Design
程序集:
System.Design.dll

获取或设置可用于预览设计时 HTML 标记的 Web 服务器控件。

public:
 property System::Web::UI::Control ^ ViewControl { System::Web::UI::Control ^ get(); void set(System::Web::UI::Control ^ value); };
public System.Web.UI.Control ViewControl { get; set; }
member this.ViewControl : System.Web.UI.Control with get, set
Public Property ViewControl As Control

属性值

Control

基类用于生成设计时 HTML 标记的 Control 对象。

示例

下面的代码示例演示如何使用 SupportsPreviewControlAttribute 属性标记控件设计器。 该代码示例从 类派生一个 Web 服务器控件， Label 并将该控件与自定义控件设计器实现相关联。 控件设计器类声明标记为 ， SupportsPreviewControl 属性设置为 true。 控件设计器替代 GetDesignTimeHtml 方法，然后在设计时以斜体显示 Text 控件的 属性。

using System;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Web.UI;
using System.Web.UI.Design;
using System.Web.UI.Design.WebControls;
using System.Web.UI.WebControls;
using System.Reflection;

namespace ControlDesignerSamples.CS
{
    // Define a simple designer associated with a 
    // simple text web control.
    
    // Mark the designer with the SupportsPreviewControlAttribute set
    // to true.  This means the base.UsePreviewControl returns true,
    // and base.ViewControl returns a temporary preview copy of the control.
    [SupportsPreviewControl(true)]
    public class SimpleTextControlDesigner : TextControlDesigner
    {		
        // Override the base GetDesignTimeHtml method to display 
        // the design time text in italics.
        public override string GetDesignTimeHtml()
        {
            string html = String.Empty;
 
            try
            {
                // Initialize the return string to the default
                // design time html of the base TextControlDesigner.
                html = base.GetDesignTimeHtml();

                // Get the ViewControl for the associated control.
                Label ctrl = (Label)ViewControl;

                ctrl.Style.Add(HtmlTextWriterStyle.FontStyle, "Italic");
                html = base.GetDesignTimeHtml();
            }
            catch (System.Exception e)
            {
               if (String.IsNullOrEmpty(html))
               {
                   html = GetErrorDesignTimeHtml(e);
               }
            }
            
            return html;
        }
    }

    // Derive a simple Web control from Label to render a text string.
    // Associate this control with the SimpleTextControlDesigner.
    [DesignerAttribute("ControlDesignerSamples.CS.SimpleTextControlDesigner"),
    ToolboxData("<{0}:MyLabelControl Runat=\"Server\"><{0}:MyLabelControl>")]
    public class MyLabelControl : Label
    {
        // Use the Label control implementation, but associate
        // the derived class with the custom control designer.
    }
}

Imports System.ComponentModel
Imports System.ComponentModel.Design
Imports System.Web.UI
Imports System.Web.UI.Design
Imports System.Web.UI.Design.WebControls
Imports System.Web.UI.WebControls
Imports System.Reflection

Namespace ControlDesignerSamples.VB

    ' Derive a simple Web control from Label to render a text string.
    ' Associate this control with the SimpleTextControlDesigner.
    <DesignerAttribute("ControlDesignerSamples.CS.SimpleTextControlDesigner"), _
    ToolboxData("<{0}:MyLabelControl Runat=""Server""><{0}:MyLabelControl>")> _
    Public Class MyLabelControl
        Inherits Label

        ' Use the Label control implementation, but associate
        ' the derived class with the custom control designer.
    End Class


    ' Mark the designer with the SupportsPreviewControlAttribute set
    ' to true.  This means the base.UsePreviewControl returns true,
    ' and base.ViewControl returns a temporary preview copy of the control.
    <SupportsPreviewControl(True)> _
    Public Class SimpleTextControlDesigner
        Inherits TextControlDesigner

        ' Override the base GetDesignTimeHtml method to display 
        ' the design time text in italics.
        Public Overrides Function GetDesignTimeHtml() As String
            Dim html As String = String.Empty

            Try
                ' Get the ViewControl for the associated control.
                Dim ctrl As Label = CType(ViewControl, Label)

                ' Set the default text, if necessary
                If ctrl.Text.Length = 0 Then
                    ctrl.Text = "Sample Text"
                End If

                ' Set the style to italic
                ctrl.Style.Add(HtmlTextWriterStyle.FontStyle, "italic")

                ' Let the base class create the HTML markup
                html = MyBase.GetDesignTimeHtml()
            Catch ex As Exception
                If String.IsNullOrEmpty(html) Then
                    ' Display the exception message
                    html = GetErrorDesignTimeHtml(ex)
                End If
            End Try

            Return html
        End Function

    End Class
End Namespace

注解

属性 ViewControl 使用 UsePreviewControl 属性来确定其返回值。

UsePreviewControl如果 属性为 true，则 ViewControl 属性返回控件的临时副本。 对临时控件的更改不会持久保存。

UsePreviewControl如果 属性为 false，则 ViewControl 属性返回 控件的 Component 属性的实例。 对控件实例的更改将持久保存。

对象 SupportsPreviewControl 中的 SupportsPreviewControlAttribute 设置用于设置 属性的值 UsePreviewControl 。 因此， SupportsPreviewControl 设置确定基ControlDesigner类中的 属性返回ViewControl的控件的类型。 SupportsPreviewControlAttribute如果未在控件设计器声明中指定 ，则ControlDesigner对象行为等效于将 SupportsPreviewControl 属性指定为 false。

适用于

另请参阅