已经有与此命令必须先关闭相关联的打开的DataReader

Question

Dim staffid = TextBox1.Text 
    Dim conn As New SqlConnection 
    conn.ConnectionString = SqlDataSource1.ConnectionString 

    Dim command1 As New SqlCommand("SELECT StaffDetails.StaffID, SUM(HolidayRequests.RequestTotalDays) AS Expr1 FROM HolidayRequests INNER JOIN StaffDetails ON HolidayRequests.Username = StaffDetails.UserName WHERE (StaffDetails.StaffID = staffID) GROUP BY StaffDetails.StaffID, HolidayRequests.ApprovalStatus HAVING (HolidayRequests.ApprovalStatus = N'approved')", conn) 
    Dim command2 As New SqlCommand() 
    conn.Open() 
    Dim rdr As SqlDataReader 
    rdr = command1.ExecuteReader 
    Dim UpdateQuery As String 
    While (rdr.Read()) 

     UpdateQuery = "UPDATE HolidayEntitlement set Holiday_Taken = @Expr1" 
     command2.Parameters.AddWithValue("@Expr1", rdr("Expr1").ToString()) 

     'run update query 

     command2.CommandText = UpdateQuery 
     command2.ExecuteNonQuery() 

     conn.Close() 
    End While 

以下错误： command2.ExecuteNonQuery：Connection属性尚未初始化。

Answer 1

嗨，你需要创建第二个命令对象。由于您正在从相同的命令对象读取数据，因此您正在尝试执行更新语句。

此外，您正在关闭while循环内的连接。之后你必须这样做。

Answer 2

创建第二个命令。换句话说，使用一个游标进行阅读，另一个用于更新。