在这个ADO.NET代码中,我的逻辑是什么？它总是返回假？

Question

这是一个简单的函数,如果用户存在于users表中,则返回TRUE,否则返回false.

由于某种原因,它总是返回false,我甚至删除了WHERE子句,我仍然得到错误？(手动检查查询分析器告诉我有很多行？)

Public Shared Function DoesUserExist(ByVal userID As Integer) As Boolean

    Dim retValue As Boolean

    retValue = False

    Using conn As New SqlConnection(GetConnectionString())

        'Dim cmd As SqlCommand = New SqlCommand("SELECT user_ID FROM users WHERE user_ID = @userID", conn)
        Dim cmd As SqlCommand = New SqlCommand("SELECT user_ID FROM users", conn)


        cmd.Parameters.Add("@userID", SqlDbType.NVarChar).Value = userID
        cmd.CommandType = CommandType.Text

        conn.Open()

        Dim reader As SqlDataReader = cmd.ExecuteReader()


        'If Not reader Is Nothing Then
        '    HttpContext.Current.Response.Write("<br>Null")
        'End If

        If reader.Read() Then

            retValue = True

        End If


        conn.Close()

        cmd.Dispose()

    End Using


    retValue = False



    Return retValue

End Function

Answer 1

您在退出之前将retValue设置为false.那就是问题所在.

这是正确的代码:

...

    If reader.Read() Then

        retValue = True

    Else

        retValue = False

    End If


    conn.Close()

    cmd.Dispose()

End Using

Return retValue

....