Question

我有这个类定义：

def test2 = Favourite.get(ids) //get the existing favourite by id
test2.users = ...              //update some properties
test2.save()

为什么这个声明会生成非抽象类？

Imports System.Data.SqlClient
Partial Class Questions
Inherits System.Web.UI.Page

Dim cmd As New SqlCommand
Dim Result As Integer = 0
Dim Question_ID As Integer = Nothing
Dim strconn As String = ConfigurationManager.ConnectionStrings("DefaultConnection").ConnectionString
Dim con As New SqlConnection(strconn)
Protected Sub rblQuestion_SelectedIndexChanged(sender As Object, e As EventArgs) Handles rblQuestion1.SelectedIndexChanged
    CheckAnswer(rblQuestion1.SelectedValue, lblQuestion1.Text)
End Sub

Private Sub CheckAnswer(ByVal Answer As String, ByVal Question As String)
    Dim RetrievedAnswer As String = Nothing

    Try
        Dim daQuestionID As New SqlDataAdapter("select Question_ID from tblQuestions where Question='" & Question & "'", con)
        Dim dsQuestionID As New Data.DataSet
        Dim dtQuestionID As New Data.DataTable

        If Not con.State = Data.ConnectionState.Open Then con.Open()
        daQuestionID.Fill(dsQuestionID)
        dtQuestionID = dsQuestionID.Tables(0)

        If Not dtQuestionID.Rows.Count <= 0 Then
            If Not IsDBNull(dtQuestionID.Rows(0).Item("Question_ID")) Then
                Question_ID = dtQuestionID.Rows(0).Item("Question_ID")

            Else
                Exit Sub
            End If
        End If
    Catch ex As Exception

    End Try

    Try
        Dim daAnswer As New SqlDataAdapter("select Answer from tblQuestions where Question_ID=" & Question_ID, con)
        Dim dsAnswer As New Data.DataSet
        Dim dtAnswer As New Data.DataTable

        If Not con.State = Data.ConnectionState.Open Then con.Open()
        daAnswer.Fill(dsAnswer)
        dtAnswer = dsAnswer.Tables(0)

        If Not dtAnswer.Rows.Count <= 0 Then
            If Not IsDBNull(dtAnswer.Rows(0).Item("Answer")) Then
                RetrievedAnswer = dtAnswer.Rows(0).Item("Answer")
            End If
        End If

        If RetrievedAnswer = Answer Then
            Try
                Dim sr As New IO.StreamReader(System.AppDomain.CurrentDomain.BaseDirectory & "\\result.txt")
                Result = sr.ReadLine
                sr.Close()
                Result = Result + 1
                Dim sw As New IO.StreamWriter(System.AppDomain.CurrentDomain.BaseDirectory & "\\result.txt")
                sw.WriteLine(Result)
                sw.Close()
            Catch ex As Exception

            End Try

        End If
    Catch ex As Exception

    End Try
End Sub
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load

    If Not IsPostBack Then
        Try
            Dim daQuestions As New SqlDataAdapter("SELECT TOP 20 * FROM tblQuestions ORDER BY NEWID()", con)
            Dim dsQuestions As New Data.DataSet
            Dim dtQuestions As New Data.DataTable

            If Not con.State = Data.ConnectionState.Open Then con.Open()
            daQuestions.Fill(dsQuestions)
            dtQuestions = dsQuestions.Tables(0)

            If Not dtQuestions.Rows.Count <= 0 Then
                'For Question 1
                If Not IsDBNull(dtQuestions.Rows(0).Item("Question")) Then
                    lblQuestion1.Text = dtQuestions.Rows(0).Item("Question")
                End If
                If Not IsDBNull(dtQuestions.Rows(0).Item("Option1")) Then
                    rblQuestion1.Items(0).Text = dtQuestions.Rows(0).Item("Option1")
                End If
                If Not IsDBNull(dtQuestions.Rows(0).Item("Option2")) Then
                    rblQuestion1.Items(1).Text = dtQuestions.Rows(0).Item("Option2")
                End If
                If Not IsDBNull(dtQuestions.Rows(0).Item("Option3")) Then
                    rblQuestion1.Items(2).Text = dtQuestions.Rows(0).Item("Option3")
                End If
                If Not IsDBNull(dtQuestions.Rows(0).Item("Option4")) Then
                    rblQuestion1.Items(3).Text = dtQuestions.Rows(0).Item("Option4")
                End If
            End If
    Catch ex As Exception

        End Try




        'con.ConnectionString = ConfigurationManager.ConnectionStrings("DefaultConnection").ConnectionString
        cmd = New SqlCommand("insert into tblQuestions (Question, Option1, Option2, Option3, Option4,) values (@question, @option1, @option2, @option3, @option4)", con)
        cmd.Parameters.AddWithValue("@question", lblQuestion1.Text)
        cmd.Parameters.AddWithValue("@option1", rblQuestion1.Text)
        cmd.Parameters.AddWithValue("@option2", rblQuestion1.Text)
        cmd.Parameters.AddWithValue("@option3", rblQuestion1.Text)
        cmd.Parameters.AddWithValue("@option4", rblQuestion1.Text)
        'cmdInsertQuestion.Parameters.AddWithValue("@answer", txtAnswer.Text)
        Try
            con.Open()
            cmd.ExecuteNonQuery()
            con.Close()
            MsgBox(" ")
            'txtAnswer.Text = ""
            rblQuestion1.Text = ""
            rblQuestion1.Text = ""
            rblQuestion1.Text = ""
            rblQuestion1.Text = ""
        Catch ex As Exception
            'ex.Message
        End Try
    End If
End Sub



Protected Sub rblQuestion1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles rblQuestion1.SelectedIndexChanged

End Sub

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click


    If Not IsPostBack Then
        Try
            Dim daQuestions As New SqlDataAdapter("SELECT TOP 20 * FROM tblQuestions ORDER BY NEWID()", con)
            Dim dsQuestions As New Data.DataSet
            Dim dtQuestions As New Data.DataTable

            If Not con.State = Data.ConnectionState.Open Then con.Open()
            daQuestions.Fill(dsQuestions)
            dtQuestions = dsQuestions.Tables(0)

            If Not dtQuestions.Rows.Count <= 0 Then
                'For Question 1
                If Not IsDBNull(dtQuestions.Rows(0).Item("Question")) Then
                    lblQuestion1.Text = dtQuestions.Rows(0).Item("Question")
                End If
                If Not IsDBNull(dtQuestions.Rows(0).Item("Option1")) Then
                    rblQuestion1.Items(0).Text = dtQuestions.Rows(0).Item("Option1")
                End If
                If Not IsDBNull(dtQuestions.Rows(0).Item("Option2")) Then
                    rblQuestion1.Items(1).Text = dtQuestions.Rows(0).Item("Option2")
                End If
                If Not IsDBNull(dtQuestions.Rows(0).Item("Option3")) Then
                    rblQuestion1.Items(2).Text = dtQuestions.Rows(0).Item("Option3")
                End If
                If Not IsDBNull(dtQuestions.Rows(0).Item("Option4")) Then
                    rblQuestion1.Items(3).Text = dtQuestions.Rows(0).Item("Option4")
                End If
            End If
        Catch ex As Exception

        End Try


    End If
End Sub

Protected Sub SqlDataSource1_Selecting(sender As Object, e As SqlDataSourceSelectingEventArgs) Handles SqlDataSource1.Selecting

End Sub
End Class

Answer 1

您需要使用CodeTypeDeclaration.TypeAttributes代替MemberAttributes：

CodeTypeDeclaration helloWorldClass = new CodeTypeDeclaration("HelloWorld") 
{
     TypeAttributes = TypeAttributes.Abstract | TypeAttributes.Public
};

如果在什么时候什么都不做，他们为什么要添加一个Attributes属性定义类型？

在documentation：

中明确指定

诸如Abstract之类的一些标志与flags的含义重叠在继承的CodeTypeDeclaration的Attributes属性中来自CodeTypeMember。 属性属性是一个副作用 CodeTypeDeclaration类继承自CodeTypeMember 类可以嵌套。 TypeAttributes属性中的标志应该是用于代替Attributes属性中的标志。

为了使用这样的继承层次结构，它们会造成轻微的混淆重复。这就是好文档很重要的原因。

使用CodeDom生成的抽象类

1 个答案: