asp.net：为什么我得到 System.Collections.Generic.List`1[System. String] 当我尝试从 asp.net 网格视图中的列表打印值时？

Question

我正在尝试创建一个会话来存储特定列的值。所以我创建了这个列表来显示选中的值，但我在另一页 System.Collections.Generic.List`1[System. String] 而不是实际值。

这是第一页的代码：

Private Sub BindGrid()
 Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("dbconnection").ConnectionString)
 con.Open()
 Dim cmd As New SqlCommand("select distinct Name,assignment_id, Description ,cod from assignments 
     INNER Join crmsLecturerXCrsSection ON crmsLecturerXCrsSection.emp_key = assignments.emp_key
     INNER Join CRMSStudentsXCrsSection ON CRMSStudentsXCrsSection.CrsSec_id = crmsLecturerXCrsSection.CrsSec_id
     INNER JOIN CRMS_CourseXSection ON CRMS_CourseXSection.CrsSec_id = CRMSStudentsXCrsSection.CrsSec_id
     INNER JOIN CRMSECTIONS ON CRMSECTIONS.SEC_ID = CRMS_CourseXSection.SEC_ID
     left JOIN crmscourses ON crmscourses.crs_id = CRMS_CourseXSection.crs_id
     INNER JOIN CRMS_CourseXSection cs ON CRMS_CourseXSection.SEC_ID = CRMSECTIONS.SEC_ID
     INNER JOIN CRMSSEMESTER ON CRMSSEMESTER.SEM_ID = CRMS_CourseXSection.SEM_ID
     where  CRMSSEMESTER.SEM_ID='1'   
     and crmsLecturerXCrsSection.emp_key='436' and crmscourses.crs_desc='" + Session("crs") + "'", con)
 Dim da As New SqlDataAdapter(cmd)
 Dim dt As New DataTable()
 da.Fill(dt)
 Dim listIDs As New List(Of String)
 Dim row As DataRow
 For Each row In dt.Rows
     listIDs.Add(row("assignment_id"))
 Next
 Session("assid") = listIDs
 cmd.Connection = con
 GridView1.DataSource = cmd.ExecuteReader()
 GridView1.DataBind()
 End Sub

这是第二页：

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Label1.Text = Session("assid").ToString()
   Dim con1 As New SqlConnection(ConfigurationManager.ConnectionStrings("dbconnection").ConnectionString)
 Dim cmd1 As New SqlCommand("select * from assignments where assignment_id ='" + String.Join(",", Session("assid")) + "'", con1)


End Sub

Answer 1

您将 List(Of String) 放入 Session("assid")，这就是您得到的结果。如果你在上面调用 ToString，你将得到类型名称，这正是你所看到的，即 "System.Collections.Generic.List'1[System.String]"。与往常一样，如果您想查看列表中的项目，则需要先将项目取出。具体如何操作取决于您要对这些项目执行的操作。例如，如果您只想显示 comma-delimited 列表中的项目，您可以这样做：

Dim ids = DirectCast(Session("assid"), List(Of String))

Label1.Text = String.Join(", ", ids)

asp.net：为什么我得到 System.Collections.Generic.List`1[System. String] 当我尝试从 asp.net 网格视图中的列表打印值时？

asp.net: why am I getting System.Collections.Generic.List`1[System. String] when I try to print values from a list in an asp.net grid view?

vb.net

sql-server

asp.net