自定义格式设置概念

实现自定义格式提供程序意味着要创建一个方法，此方法将返回已格式化的字符串，并把原有值和格式字符串作为参数。这样就能实现格式设置逻辑，但是这可以为您提供无限的潜能。要激活自定义格式设置，需把 FormatInfo.FormatType 属性设置为 FormatType.Custom，把 FormatInfo.Format 属性设置为自定义格式提供程序对象。

要创建一个自定义格式提供程序对象，你需要遵照下列步骤：

创建一个实现 IFormatProvider 接口的类。此接口声明了一个单独的 GetFormat 方法，此方法必须返回一个实现 ICustomFormatter 接口的对象引用。注意，提供一个实现 IFormatProvider 和 ICustomFormatter 接口的类 —— 是一种公共惯例。在这种情况下， GetFormat 方法必须只返回一个对当前类接口的引用。
实现 ICustomFormatter 接口的 Format 方法。此方法将格式字符串、值、格式提供程序作为参数，并且必须返回设置了格式的字符串。格式设置逻辑必须在此方法中实现。
初始化 FormatInfo.Format 属性，指派一个实现了 IFormatProvider 接口的对象到该属性。参阅支持格式设置机制的成员主题，了解关于如何访问此属性的信息。

要提供一个自定义格式提供程序所需要编写的代码轮廓在下面给出：

C#	复制代码
// implementing a custom formatter object class CustomFormatter : IFormatProvider, ICustomFormatter { // implementing the GetFormat method of the IFormatProvider interface public object GetFormat(System.Type type) { return this; } // implementing the Format method of the ICustomFormatter interface public string Format(string format, object arg, IFormatProvider formatProvider) { // implement formatting logic here - this method must return the formatted string // format and args parameters specify the format string and the original value respectively // ... } } // assigning the custom formatter textEdit1.Properties.DisplayFormat.Format = new CustomFormatter(); textEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom;

复制代码

// implementing a custom formatter object
class CustomFormatter : IFormatProvider, ICustomFormatter {
   // implementing the GetFormat method of the IFormatProvider interface
   public object GetFormat(System.Type type) {
      return this;
   }
   // implementing the Format method of the ICustomFormatter interface
   public string Format(string format, object arg, IFormatProvider formatProvider) {
      // implement formatting logic here - this method must return the formatted string
      // format and args parameters specify the format string and the original value respectively
      // ...
   }
}

// assigning the custom formatter
textEdit1.Properties.DisplayFormat.Format = new CustomFormatter();
textEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom;

Visual Basic	复制代码
' implementing a custom formatter object Class CustomFormatter : Implements IFormatProvider, ICustomFormatter ' implementing the GetFormat method of the IFormatProvider interface Public Function GetFormat(ByVal type As Type) As Object Implements IFormatProvider.GetFormat Return Me End Function ' implementing the Format method of the ICustomFormatter interface Public Function Format(ByVal formatString As String, ByVal arg As Object, _ ByVal formatProvider As IFormatProvider) As String Implements ICustomFormatter.Format ' implement formatting logic here - this method must return the formatted string ' format and args parameters specify the format string and the original value respectively ' ... End Function End Class ' assigning the custom formatter TextEdit1.Properties.DisplayFormat.Format = New CustomFormatter() TextEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom

Visual Basic

复制代码

' implementing a custom formatter object
Class CustomFormatter : Implements IFormatProvider, ICustomFormatter
    ' implementing the GetFormat method of the IFormatProvider interface
    Public Function GetFormat(ByVal type As Type) As Object Implements IFormatProvider.GetFormat
        Return Me
    End Function
    ' implementing the Format method of the ICustomFormatter interface
    Public Function Format(ByVal formatString As String, ByVal arg As Object, _
      ByVal formatProvider As IFormatProvider) As String Implements ICustomFormatter.Format
        ' implement formatting logic here - this method must return the formatted string
        ' format and args parameters specify the format string and the original value respectively
        ' ...
    End Function
End Class

' assigning the custom formatter
TextEdit1.Properties.DisplayFormat.Format = New CustomFormatter()
TextEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom

下面的两个分段提供了关于创建自定义格式提供程序类的示例：一个简单的大写/小写字母示例，然后是一个十进制数以二进制形式显示的示例。

注意
仅在有必要时才使用自定义格式提供程序，因为它的性能没有标准格式提供程序的性能好。

示例 - 改变字符串值的大小写

这个示例创建了一个修改编辑器文本大小写的自定义格式提供程序。编辑器将遵照指定的格式字符串来显示文本 (FormatInfo.FormatString 属性值)。这个字符串被作为格式参数传递到 Format 方法。如果这个参数值是 'u'，那么显示值被转换为大写；如果这个格式字符串是 'l'，那么显示值被转换为小写。

参阅自定义格式设置主题，了解关于创建自定义格式提供程序的信息。

下面的插图展示了文本编辑器的、在执行示例代码之前和之后的外观。

C#	复制代码
// A custom formatter object. class CustomFormatter : IFormatProvider, ICustomFormatter{ // The GetFormat method of the IFormatProvider interface. // This must return an object that provides formatting services for the specified type. public object GetFormat(System.Type type){ return this; } // The Format method of the ICustomFormatter interface. // This must format the specified value according to the specified format settings. public string Format(string format, object arg, IFormatProvider formatProvider){ string formatValue = arg.ToString(); if (format == "u") return formatValue.ToUpper(); else if (format == "l") return formatValue.ToLower(); else return formatValue; } } // ... // Assign the custom formatter to the editors. textEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom; textEdit1.Properties.DisplayFormat.FormatString = "u"; textEdit1.Properties.DisplayFormat.Format = new CustomFormatter(); textEdit2.Properties.DisplayFormat.FormatType = FormatType.Custom; textEdit2.Properties.DisplayFormat.FormatString = "l"; textEdit2.Properties.DisplayFormat.Format = new CustomFormatter();

复制代码

// A custom formatter object.
class CustomFormatter : IFormatProvider, ICustomFormatter{
    // The GetFormat method of the IFormatProvider interface.
    // This must return an object that provides formatting services for the specified type.
    public object GetFormat(System.Type type){
        return this;
    }
    // The Format method of the ICustomFormatter interface.
    // This must format the specified value according to the specified format settings.
    public string Format(string format, object arg, IFormatProvider formatProvider){
        string formatValue = arg.ToString();
        if (format == "u")
            return formatValue.ToUpper();
        else if (format == "l")
            return formatValue.ToLower();
        else return formatValue;
    }
}
// ...
// Assign the custom formatter to the editors.
textEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom;
textEdit1.Properties.DisplayFormat.FormatString = "u";
textEdit1.Properties.DisplayFormat.Format = new CustomFormatter();

textEdit2.Properties.DisplayFormat.FormatType = FormatType.Custom;
textEdit2.Properties.DisplayFormat.FormatString = "l";
textEdit2.Properties.DisplayFormat.Format = new CustomFormatter();

Visual Basic	复制代码
' A custom formatter object. Class CustomFormatter : Implements IFormatProvider, ICustomFormatter ' The GetFormat method of the IFormatProvider interface. ' This must return an object that provides formatting services for the specified type. Public Function GetFormat(ByVal type As Type) As Object _ Implements IFormatProvider.GetFormat Return Me End Function ' The Format method of the ICustomFormatter interface. ' This must format the specified value according to the specified format settings. Public Function Format(ByVal formatString As String, ByVal arg As Object, _ ByVal formatProvider As IFormatProvider) As String Implements ICustomFormatter.Format Dim formatValue As String = arg.ToString() If (formatString = "u") Then Format = formatValue.ToUpper() ElseIf formatString = "l" Then Format = formatValue.ToLower() Else Format = formatValue End If End Function End Class ' ... ' Assign the custom formatter to the editors. TextEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom TextEdit1.Properties.DisplayFormat.FormatString = "u" TextEdit1.Properties.DisplayFormat.Format = New CustomFormatter() TextEdit2.Properties.DisplayFormat.FormatType = FormatType.Custom TextEdit2.Properties.DisplayFormat.FormatString = "l" TextEdit2.Properties.DisplayFormat.Format = New CustomFormatter()

Visual Basic

复制代码

' A custom formatter object.
Class CustomFormatter : Implements IFormatProvider, ICustomFormatter
    ' The GetFormat method of the IFormatProvider interface.
    ' This must return an object that provides formatting services for the specified type.
    Public Function GetFormat(ByVal type As Type) As Object _
    Implements IFormatProvider.GetFormat
        Return Me
    End Function
    ' The Format method of the ICustomFormatter interface.
    ' This must format the specified value according to the specified format settings.
    Public Function Format(ByVal formatString As String, ByVal arg As Object, _
    ByVal formatProvider As IFormatProvider) As String Implements ICustomFormatter.Format
        Dim formatValue As String = arg.ToString()
        If (formatString = "u") Then
            Format = formatValue.ToUpper()
        ElseIf formatString = "l" Then
            Format = formatValue.ToLower()
        Else
            Format = formatValue
        End If
    End Function
End Class
' ...
' Assign the custom formatter to the editors.
TextEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom
TextEdit1.Properties.DisplayFormat.FormatString = "u"
TextEdit1.Properties.DisplayFormat.Format = New CustomFormatter()

TextEdit2.Properties.DisplayFormat.FormatType = FormatType.Custom
TextEdit2.Properties.DisplayFormat.FormatString = "l"
TextEdit2.Properties.DisplayFormat.Format = New CustomFormatter()

示例 - 以二进制形式显示十进制值

这个示例展示了如何创建一个自定义格式提供程序对象，它以二进制形式显示十进制值，但是仅当格式字符串被设置为“B”时才这样显示。请参阅自定义格式设置主题，了解关于创建自定义格式提供程序的信息。

结果如下图所示。

C#	复制代码
// A custom formatter object. public class BaseFormatter : IFormatProvider, ICustomFormatter { // The GetFormat method of the IFormatProvider interface. // This must return an object that provides formatting services for the specified type. public object GetFormat(Type format) { if (format == typeof (ICustomFormatter)) return this; else return null; } // The Format method of the ICustomFormatter interface. // This must format the specified value according to the specified format settings. public string Format (string format, object arg, IFormatProvider provider) { if (format == null) { if (arg is IFormattable) return ((IFormattable)arg).ToString(format, provider); else return arg.ToString(); } if (format == "B") return Convert.ToString(Convert.ToInt32(arg), 2); else return arg.ToString(); } } // ... // Assign the custom formatter to the editor. spinEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom; spinEdit1.Properties.DisplayFormat.FormatString = "B"; spinEdit1.Properties.DisplayFormat.Format = new BaseFormatter(); spinEdit1.Properties.IsFloatValue = false; spinEdit1.EditValue = 10;

复制代码

// A custom formatter object.
public class BaseFormatter : IFormatProvider, ICustomFormatter {
    // The GetFormat method of the IFormatProvider interface.
    // This must return an object that provides formatting services for the specified type.
    public object GetFormat(Type format) {
        if (format == typeof (ICustomFormatter)) return this;
        else return null;
    }
    // The Format method of the ICustomFormatter interface.
    // This must format the specified value according to the specified format settings.
    public string Format (string format, object arg, IFormatProvider provider) {
        if (format == null) {
            if (arg is IFormattable)
                return ((IFormattable)arg).ToString(format, provider);
            else
                return arg.ToString(); 
        }
        if (format == "B")
            return Convert.ToString(Convert.ToInt32(arg), 2);
        else
            return arg.ToString();
    }
}

// ...
// Assign the custom formatter to the editor.
spinEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom;
spinEdit1.Properties.DisplayFormat.FormatString = "B";
spinEdit1.Properties.DisplayFormat.Format = new BaseFormatter();
spinEdit1.Properties.IsFloatValue = false;
spinEdit1.EditValue = 10;

Visual Basic	复制代码
' A custom formatter object. Public Class BaseFormatter : Implements IFormatProvider, ICustomFormatter ' The GetFormat method of the IFormatProvider interface. ' This must return an object that provides formatting services for the specified type. Public Function GetFormat(ByVal format As Type) As Object _ Implements IFormatProvider.GetFormat If format.ToString() = GetType(ICustomFormatter).ToString() Then GetFormat = Me Else GetFormat = Nothing End If End Function ' The Format method of the ICustomFormatter interface. ' This must format the specified value according to the specified format settings. Public Function Format(ByVal formatString As String, ByVal arg As Object, _ ByVal provider As IFormatProvider) As String Implements ICustomFormatter.Format If (formatString = Nothing) Then If TypeOf arg Is IFormattable Then Format = CType(arg, IFormattable).ToString(formatString, provider) Else Format = arg.ToString() End If Exit Function End If If (formatString = "B") Then Format = Convert.ToString(Convert.ToInt32(arg), 2) Else Format = arg.ToString() End If End Function End Class ' ... ' Assign the custom formatter to the editor. SpinEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom SpinEdit1.Properties.DisplayFormat.FormatString = "B" SpinEdit1.Properties.DisplayFormat.Format = New BaseFormatter() SpinEdit1.Properties.IsFloatValue = False SpinEdit1.EditValue = 10

Visual Basic

复制代码

' A custom formatter object.
Public Class BaseFormatter : Implements IFormatProvider, ICustomFormatter
    ' The GetFormat method of the IFormatProvider interface.
    ' This must return an object that provides formatting services for the specified type.
    Public Function GetFormat(ByVal format As Type) As Object _
    Implements IFormatProvider.GetFormat
        If format.ToString() = GetType(ICustomFormatter).ToString() Then
            GetFormat = Me
        Else
            GetFormat = Nothing
        End If
    End Function

    ' The Format method of the ICustomFormatter interface.
    ' This must format the specified value according to the specified format settings.
    Public Function Format(ByVal formatString As String, ByVal arg As Object, _
    ByVal provider As IFormatProvider) As String Implements ICustomFormatter.Format
        If (formatString = Nothing) Then
            If TypeOf arg Is IFormattable Then
                Format = CType(arg, IFormattable).ToString(formatString, provider)
            Else
                Format = arg.ToString()
            End If
            Exit Function
        End If
        If (formatString = "B") Then
            Format = Convert.ToString(Convert.ToInt32(arg), 2)
        Else
            Format = arg.ToString()
        End If
    End Function
End Class

' ...
' Assign the custom formatter to the editor.
SpinEdit1.Properties.DisplayFormat.FormatType = FormatType.Custom
SpinEdit1.Properties.DisplayFormat.FormatString = "B"
SpinEdit1.Properties.DisplayFormat.Format = New BaseFormatter()
SpinEdit1.Properties.IsFloatValue = False
SpinEdit1.EditValue = 10