将记录检索到 vb.net 中的组合框

Question

我有一个存储过程，我想将记录显示到combobox。但它说

此行的位置 0 处没有行。

cboSchoolYear.Text = (dt.Rows(0)("Schoolyear")) 

存储过程代码：

ALTER PROCEDURE [dbo].[uspLatestDateEnrolled]
    -- Add the parameters for the stored procedure here

@studID INT


AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    -- Insert statements for procedure here
    SELECT TOP 1 DateEnrolled as LatestDate,
    SchoolYear,Levels,Section,StudentID
    FROM StudentHistory
    WHERE studentID = @studID
    ORDER BY DateEnrolled DESC
END

vb.net代码

   cn.Open()
        Using cmd As New SqlClient.SqlCommand("uspLatestDateEnrolled", cn)
            cmd.CommandType = CommandType.StoredProcedure
            cmd.Parameters.Add(New SqlParameter("@studID", frmView.dgv1.SelectedCells(0).Value))
            cboSchoolYear.Text = (dt.Rows(0)("Schoolyear"))
            cboGradeLevel.Text = (dt.Rows(1)("levels"))
            cboSection.Text = (dt.Rows(2)("Section"))
            dtpEnrollment.Text = (dt.Rows(3)("dateEnrolled"))
        End Using
        cn.Close()

Answer 1

在做一些研究时，这段代码解决了我的问题。感谢 Codexer，给了我一些建议。

  Try
        cn.Open()
        cmd = New SqlCommand("uspLatestDateEnrolled", cn)
        cmd.Parameters.AddWithValue("@studID", frmView.dgv1.SelectedCells(0).Value)
        cmd.CommandType = CommandType.StoredProcedure
        da.SelectCommand = cmd
        da.Fill(dt)
        cboSchoolYear.Text = dt.Rows(0).Item("SchoolYear")
        cboGradeLevel.Text = dt.Rows(0).Item("levels")
        cboSection.Text = dt.Rows(0).Item("Section")
        dtpEnrollment.Text = dt.Rows(0).Item("DateEnrolled")

    Catch x As Exception
        MessageBox.Show(x.GetBaseException().ToString(), "Error", MessageBoxButtons.OK, MessageBoxIcon.[Error])
    Finally
        cmd.Dispose()
        cn.Close()
    End Try

Answer 2

您这里有几处错误（或几处错误并且帖子中缺少几处）

1. 你永远不会声明 DT
2. 如果您返回的结果不止一个，则您正在跳行（您不会因为 sql 中的前 1 个结果而从不同的记录中获取信息）
3. 您不检查是否从数据库返回任何内容

您的 vb.net 代码应如下所示（此代码并不完美，但它应该让您朝着正确的方向前进）

    cn.Open()
    Using cmd As New SqlClient.SqlCommand("uspLatestDateEnrolled", cn)
        cmd.CommandType = CommandType.StoredProcedure
        cmd.Parameters.Add(New SqlParameter("@studID", frmView.dgv1.SelectedCells(0).Value))

    Dim SQLDataReader as SQLDataReader = cmd.executeReader()

    if sqldatareader.hasrows = true then 
    while sqldatareader.read

        if sqldatareader("Schoolyear") isnot dbnull.value then 
                cboSchoolYear.Text = sqldatareader("Schoolyear")
        else
                cboSchoolYear.Text = "Null"
        end if
        if sqldatareader("levels") isnot dbnull.value then 
                cboGradeLevel.Text = sqldatareader("levels")
        else
                cboGradeLevel.Text = "Null"
        end if
        if sqldatareader("Section") isnot dbnull.value then 
                cboSection.Text = sqldatareader("Section")
        else
                cboSection.Text = "Null"
        end if
        if sqldatareader("dateEnrolled") isnot dbnull.value then 
                cboSection.Text = sqldatareader("dateEnrolled")
        else
                cboSection.Text = "Null"
        end if

    loop
    else
       'No Results
    end if 

    End Using
    cn.Close()