asp.net – 如何使用Linq获取XML元素的值,即使是空的

其次,您可以像这样使用Element属性和Value属性：

staffBio = staff.Element("staffBio").Value

工作人员只有一个staffBio元素,因此不需要使用Descendants属性.值是一个字符串,因此您不需要调用Value.ToString.如果元素为空,则Value将返回一个空字符串,这正是您要查找的内容！

第三,在VB.NET中有一个更好的(我相信更直接)的方式.这是一个控制台应用程序,演示了我将如何做到这一点：

Module Module1

Sub Main()
    Dim myXMLFile = <allStaff>
                        <staff>
                            <staffName>Test Staff</staffName>
                            <staffTitle>Slave</staffTitle>
                            <staffDepartmentName>Finance</staffDepartmentName>
                            <staffOffice>London</staffOffice>
                            <staffEmail>t.staff@battens.co.uk</staffEmail>
                            <staffPhone>0207 123 456</staffPhone>
                            <staffNotes>Working hours Mon to Thurs 9.15 - 5.15</staffNotes>
                            <staffBio></staffBio>
                        </staff>
                        <staff>
                            <staffName>Other Staff</staffName>
                            <staffTitle>Master</staffTitle>
                            <staffDepartmentName>IT</staffDepartmentName>
                            <staffOffice>Oxford</staffOffice>
                            <staffEmail>o.staff@battens.co.uk</staffEmail>
                            <staffPhone>0207 123 789</staffPhone>
                            <staffNotes></staffNotes>
                            <staffBio>Some guy.</staffBio>
                        </staff>
                    </allStaff>

    Dim search = "Test"

    Dim searchQuery = From staff In myXMLFile...<staff> _
                      Where staff.<staffName>.Value.Contains(search) _
                      Select si = New StaffInfo With {.Name = staff.<staffName>.Value,_
                                                      .Title = staff.<staffTitle>.Value,_
                                                      .Department = staff.<staffDepartmentName>.Value,_
                                                      .Office = staff.<staffOffice>.Value,_
                                                      .Email = staff.<staffEmail>.Value,_
                                                      .Phone = staff.<staffPhone>.Value,_
                                                      .Notes = staff.<staffNotes>.Value,_
                                                      .Bio = staff.<staffBio>.Value}

    For Each staff In searchQuery
        Console.WriteLine("Name: {0}",staff.Name)
        Console.WriteLine("Title: {0}",staff.Title)
        Console.WriteLine("Department: {0}",staff.Department)
        Console.WriteLine("Office: {0}",staff.Office)
        Console.WriteLine("Email: {0}",staff.Email)
        Console.WriteLine("Phone: {0}",staff.Phone)
        Console.WriteLine("Notes: {0}",staff.Notes)
        Console.WriteLine("Bio: {0}",staff.Bio)
        Console.WriteLine()
    Next

    Console.ReadLine()

End Sub

Private Class StaffInfo

    Private _name As String
    Public Property Name() As String
        Get
            Return _name
        End Get
        Set(ByVal value As String)
            _name = value
        End Set
    End Property

    Private _title As String
    Public Property Title() As String
        Get
            Return _title
        End Get
        Set(ByVal value As String)
            _title = value
        End Set
    End Property

    Private _department As String
    Public Property Department() As String
        Get
            Return _department
        End Get
        Set(ByVal value As String)
            _department = value
        End Set
    End Property

    Private _office As String
    Public Property Office() As String
        Get
            Return _office
        End Get
        Set(ByVal value As String)
            _office = value
        End Set
    End Property

    Private _email As String
    Public Property Email() As String
        Get
            Return _email
        End Get
        Set(ByVal value As String)
            _email = value
        End Set
    End Property

    Private _phone As String
    Public Property Phone() As String
        Get
            Return _phone
        End Get
        Set(ByVal value As String)
            _phone = value
        End Set
    End Property

    Private _notes As String
    Public Property Notes() As String
        Get
            Return _notes
        End Get
        Set(ByVal value As String)
            _notes = value
        End Set
    End Property

    Private _bio As String
    Public Property Bio() As String
        Get
            Return _bio
        End Get
        Set(ByVal value As String)
            _bio = value
        End Set
    End Property

End Class

End Module

如果您有XML的模式(.xsd文件),那么您可以将对该xmlns的引用导入VB源文件,这将为您提供用于编写??LINQ to XML查询的智能感知.

(编辑：创建模式的一种快捷方法是在Visual Studio中打开XML文件,然后从XML菜单中选择“创建模式”.)

有关更多信息和帮助,请查看“How Do I” video series on LINQ by Beth Massi.