FontNamesConverter.CanConvertFrom(ITypeDescriptorContext, Type) 方法

定义

确定此转换器是否可以将指定数据类型的对象转换为包含个别字体名称的字符串数组。Determines whether this converter can convert an object of the specified data type to an array of strings containing individual font names.

public:
 override bool CanConvertFrom(System::ComponentModel::ITypeDescriptorContext ^ context, Type ^ sourceType);
public override bool CanConvertFrom (System.ComponentModel.ITypeDescriptorContext context, Type sourceType);
override this.CanConvertFrom : System.ComponentModel.ITypeDescriptorContext * Type -> bool
Public Overrides Function CanConvertFrom (context As ITypeDescriptorContext, sourceType As Type) As Boolean

参数

context
ITypeDescriptorContext

提供类型转换器上下文信息的 ITypeDescriptorContext 对象。A ITypeDescriptorContext object that provides information about the context of a type converter. 可以选择为该参数传入 nullYou can optionally pass in null for this parameter.

sourceType
Type

表示要从中转换的数据类型的 TypeA Type that represents the data type to convert from.

返回

如果可以转换类型,则为 true;否则为 falsetrue if the type can be converted; otherwise, false.

示例

下面的代码示例演示如何使用 CanConvertFrom 方法。The following code example demonstrates how to use the CanConvertFrom method. 此示例在执行转换之前, 确定指定的数据类型是否可以转换为包含单个字体名称的字符串数组。The example determines whether the specified data type can be converted to an array of strings that contains the individual font names before performing the conversion.

<%@ Page Language="C#" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>FontNamesConverter Example</title>
<script language="C#" runat="server">

      void Page_Load(Object sender, EventArgs e) 
      {

         // Declare local variables.
         System.Globalization.CultureInfo culture = new System.Globalization.CultureInfo("en");
         System.ComponentModel.ITypeDescriptorContext context = null;
         Object names; 
         Object name_string;

         // Create FontNamesConverter object.
         FontNamesConverter fontconverter = new FontNamesConverter();

         // Create original list of fonts.
         string font_list = "arial, times new roman, verdana";

         // Check for type compatibility.
         if (fontconverter.CanConvertFrom(context, typeof(string)))
         {

            // Display original string.
            Label1.Text = "Original String :" + "<br /><br />" + font_list;

            // Convert string to array to strings and display results.
            names = fontconverter.ConvertFrom(context, culture, font_list);
            Label2.Text = "Converted to Array of Strings : " + "<br /><br />";
            foreach (string name_element in (string[])names)
            {
               Label2.Text += name_element + "<br />";
            }

            // Convert array of strings back to a string and display results.
            name_string = fontconverter.ConvertTo(context, culture, names, typeof(string)); 
            Label3.Text = "Converted back to String :" + "<br /><br />" + (string)name_string;

         }
          
      }

   </script>

</head>
<body>

   <h3>FontNamesConverter Example</h3>
   <br />

   <form id="form1" runat="server">
        
      <asp:Label id="Label1" runat="server"/>
      <br /><hr />
      <asp:Label id="Label2" runat="server"/>
      <br /><hr />
      <asp:Label id="Label3" runat="server"/>
        
   </form>

</body>
</html>
   
<%@ Page Language="VB" AutoEventWireup="True" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>FontNamesConverter Example</title>
<script language="VB" runat="server">
    Sub Page_Load(sender As Object, e As EventArgs)
        
        ' Declare local variables.
        Dim culture As New System.Globalization.CultureInfo("en")
        Dim context As System.ComponentModel.ITypeDescriptorContext = Nothing
        Dim names As Object
        Dim name_string As Object
        
        ' Create FontNamesConverter object.
        Dim fontconverter As New FontNamesConverter()
        
        ' Create original list of fonts.
        Dim font_list As String = "arial, times new roman, verdana"
        
        ' Check for type compatibility.
        If fontconverter.CanConvertFrom(context, GetType(String)) Then
            
            ' Display original string.
            Label1.Text = "Original String :" & "<br /><br />" & font_list
            
            ' Convert string to array to strings and display results.
            names = fontconverter.ConvertFrom(context, culture, font_list)
            Label2.Text = "Converted to Array of Strings : " & "<br /><br />"
            Dim name_element As String
            For Each name_element In CType(names, String())
                Label2.Text &= name_element & "<br />"
            Next name_element
            
            ' Convert array of strings back to a string and display results.
            name_string = fontconverter.ConvertTo(context, culture, names, _
                GetType(String))
            Label3.Text = "Converted back to String :" & "<br /><br />" & _
                CType(name_string, String)
        End If 
    End Sub 'Page_Load
  </script>

</head>
<body>

   <h3>FontNamesConverter Example</h3>
   <br />

   <form id="form1" runat="server">
        
      <asp:Label id="Label1" runat="server"/>
      <br /><hr />
      <asp:Label id="Label2" runat="server"/>
      <br /><hr />
      <asp:Label id="Label3" runat="server"/>
        
   </form>

</body>
</html>
   

注解

CanConvertFrom使用方法可确定指定的数据类型是否可转换为包含单个字体名称的字符串数组。Use the CanConvertFrom method to determine whether the specified data type can be converted to an array of strings containing individual font names.

备注

此转换器只能从string数据类型转换。This converter can convert only from a string data type. 参数的类型String必须为。 sourceTypeThe sourceType parameter must be of type String. 否则, 此方法将false返回以指示无法转换指定的数据类型。Otherwise, this method returns false to indicate that the specified data type cannot be converted.

您可以选择性地传入null context参数。You can optionally pass in null for the context parameter.

适用于

另请参阅