Question

我正在尝试从Wpf Tuturial

学习WPF

我在WPF和VB.Net中遇到转换问题。我正在使用VS 2012

这是我的XML代码

<Window x:Class="Binding_Sample_Converter"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-Namespace:WPF_Tutorial.WPFTutorials.Converter"  
Title="Binding_Sample_Converter" Height="300" Width="300">
<Window.Resources>
    <!--
    Error   1   The name "YesNo" does not exist in the namespace "clr-Namespace:WPF_Tutorial.WPFTutorials.Converter".
    Error   2   The name "YesNo" does not exist in the namespace "clr-Namespace:WPF_Tutorial.WPFTutorials.Converter".
    Error   3   The type 'local:YesNo' was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built.

    -->
    <local:YesNo x:Key="YesNo" />
</Window.Resources>
<Grid>

</Grid>

这是我的VB.Net代码

Imports System.Windows
Imports System.ComponentModel
Imports System.Windows.Data
Namespace WPFTutorials.Converter
    Public Class Binding_Sample_Converter
        Public Class YesNo
        Implements IValueConverter

        Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As Globalization.CultureInfo) As Object Implements IValueConverter.Convert
            Select Case value.ToString.ToLower
                Case "yes"
                    Return True
                Case "no"
                    Return False
            End Select
            Return False
        End Function

        Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack
            If TypeOf value Is Boolean Then
                If CBool(value) = True Then : Return "yes"
                Else : Return "no"
                End If
            Else : Return "no"
            End If
        End Function
    End Class
End Class
End Namespace

我正在尝试将C＃代码从所述网站教程转换为VB.Net

Err是

        Error   1   The name "YesNo" does not exist in the namespace "clr-Namespace:WPF_Tutorial.WPFTutorials.Converter".
    Error   2   The name "YesNo" does not exist in the namespace "clr-Namespace:WPF_Tutorial.WPFTutorials.Converter".
    Error   3   The type 'local:YesNo' was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built.

请帮助

提前致谢

Amit Saraf

编辑。呃。＆安培;修改后警告

        <!--
    Warning 1   Namespace or type specified in the Imports 'WPFTutorials.Converter' doesn't contain any public member or cannot be found. Make sure the namespace or the type is defined and contains at least one public member. Make sure the imported element name doesn't use any aliases.  D:\Data - 2012\WPF\WPF_Tutotrial\obj\Debug\Binding_Sample_Converter.g.i.vb  35  9   WPF_Tutotrial
    Error   2   The name "YesNo" does not exist in the namespace "clr-namespace:WPFTutorials.Converter".    D:\Data - 2012\WPF\WPF_Tutotrial\Binding_Sample_Converter.xaml  11  9   WPF_Tutotrial
    Error   3   The type 'local:YesNo' was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built. D:\Data - 2012\WPF\WPF_Tutotrial\Binding_Sample_Converter.xaml  12  10  WPF_Tutotrial
    -->

Answer 1

您的代码中存在两个问题。

首先，命名空间名称区分大小写。 N应该是小写的。名称空间声明的语法是clr-namespace。

嵌套类YesNo中的第二个，Binding_Sample_Converter类，它不应该是。{你can't create an instance of nested class in XAML。来自MSDN：

为了能够被实例化为对象元素，你的   班级必须符合以下要求：



您的自定义类必须   公开并支持默认（无参数）公共构造函数。



您的自定义   class不能是嵌套类。嵌套类和“点”   它们的一般CLR使用语法会干扰其他WPF和/或XAML   附加属性等功能。

XAML ：

xmlns:local="clr-namespace:WPFTutorials.Converter"

转换器：

将YesNo类移出类Public Class Binding_Sample_Converter并直接在命名空间下声明。

Namespace WPFTutorials.Converter
   Public Class Binding_Sample_Converter
   End Class

Public Class YesNo
    Implements IValueConverter

    Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As Globalization.CultureInfo) As Object Implements IValueConverter.Convert
        Select Case value.ToString.ToLower
            Case "yes"
                Return True
            Case "no"
                Return False
        End Select
        Return False
    End Function

    Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack
        If TypeOf value Is Boolean Then
            If CBool(value) = True Then : Return "yes"
            Else : Return "no"
            End If
        Else : Return "no"
        End If
    End Function
  End Class
End Namespace

名称空间“YesNo”在命名空间“clr-Namespace：WPF_Tutorial.WPFTutorials.Converter”中不存在

1 个答案: