SQL 插入多行，对象引用未设置为对象错误的实例

Question

我对如何使用 SQL 数据库还很陌生，我在这方面的代码目标是制作一个 do 循环，该循环将不断读取当月创建的文件并将其插入到各自的文件中SQL 数据库中的列。如果有一个简单的错误请原谅我，这是我的基于 theatre/cinema 的课程作业。除了它显示的明显错误 "Object reference is not set to an instance of an object" 之外，我似乎无法找出错误，非常感谢帮助，谢谢！

SpecificPath() 从硬盘驱动器检索文件并从它访问的文本文件中读取特定行。

   Do Until C = 32

            If File.Exists(SearchPath(C)) Then
                Dim sr As New StreamReader(SearchPath(C))
                Items(1, C) = ReadSpecificLine(SearchPath(C), 14) 'Total Product Profit
                Items(2, C) = ReadSpecificLine(SearchPath(C), 15) 'Total Ticket Profit
                Items(3, C) = ReadSpecificLine(SearchPath(C), 16) 'Total Profit from Water
                Items(4, C) = ReadSpecificLine(SearchPath(C), 17) 'Total Profit from Large Soft Drink
                Items(5, C) = ReadSpecificLine(SearchPath(C), 18) 'Total Profit from Small Soft Drink
                Items(6, C) = ReadSpecificLine(SearchPath(C), 19) 'Total Profit from Buttered Popcorn
                Items(7, C) = ReadSpecificLine(SearchPath(C), 20) 'Total Profit from Salted Popcorn
                Items(8, C) = ReadSpecificLine(SearchPath(C), 21) 'Total Profit from Sweet Popcorn
                Items(9, C) = ReadSpecificLine(SearchPath(C), 28) 'Total Profit from Adult Tickets
                Items(10, C) = ReadSpecificLine(SearchPath(C), 29) 'Total Profit from Teen Tickets
                Items(11, C) = ReadSpecificLine(SearchPath(C), 30) 'Total Profit from Child Tickets
                Items(12, C) = ReadSpecificLine(SearchPath(C), 34) 'Gross Profit
                Items(13, C) = ReadSpecificLine(SearchPath(C), 35) 'Net Profit

                MySqlConn = New MySqlConnection
                Try
                    MySqlConn.ConnectionString = "Placeholder for pasting onto website"
                    MySqlConn.Open()
                    cmd.Connection = MySqlConn
                    cmd.CommandText = "INSERT INTO Cinema_Graph_Data (Year,Month,Water,Large_SD,Small_SD,Buttered_Popcorn,Salted_Popcorn,Sweet_Popcorn,Adult_Tickets,Teen_Tickets,Child_Tickets,Products_Profit,Ticket_Profit,Gross_Profit,Net_Profit) VALUES(@year,@month,@water,@largeSD,@smallSD,@buttered,@salted,@sweet,@adult,@teen,@child,@product,@ticket,@gross,@net)"
                    cmd.Parameters.Add("@year", MySqlDbType.VarChar).Value = Year
                    cmd.Parameters.Add("@month", MySqlDbType.VarChar).Value = Month
                    cmd.Parameters.Add("@water", MySqlDbType.VarChar).Value = Items(3, C)
                    cmd.Parameters.Add("@largeSD", MySqlDbType.VarChar).Value = Items(4, C)
                    cmd.Parameters.Add("@smallSD", MySqlDbType.VarChar).Value = Items(5, C)
                    cmd.Parameters.Add("@buttered", MySqlDbType.VarChar).Value = Items(6, C)
                    cmd.Parameters.Add("@salted", MySqlDbType.VarChar).Value = Items(7, C)
                    cmd.Parameters.Add("@sweet", MySqlDbType.VarChar).Value = Items(8, C)
                    cmd.Parameters.Add("@adult", MySqlDbType.VarChar).Value = Items(9, C)
                    cmd.Parameters.Add("@teen", MySqlDbType.VarChar).Value = Items(10, C)
                    cmd.Parameters.Add("@child", MySqlDbType.VarChar).Value = Items(11, C)
                    cmd.Parameters.Add("@product", MySqlDbType.VarChar).Value = Items(1, C) 'This is product profit - employee form saves data in file first
                    cmd.Parameters.Add("@ticket", MySqlDbType.VarChar).Value = Items(2, C) 'This is ticket profit - employee form saves data in file second then its water
                    cmd.Parameters.Add("@gross", MySqlDbType.VarChar).Value = Items(12, C)
                    cmd.Parameters.Add("@net", MySqlDbType.VarChar).Value = Items(13, C)
                    cmd.ExecuteNonQuery()
                Catch ex As Exception
                    MessageBox.Show("Error while inserting record on table..." & ex.Message, "Insert Records")
                Finally
                    MySqlConn.Close()
                    sr.Close()
                End Try
            ElseIf C = 31 Then
                MsgBox("Imported Data From " & MonthName(Month, True) & " " & Year & vbNewLine & "Successfully uploaded data to SQL Database.")

            End If
    C = C + 1
        Loop
    Else
        MsgBox("Please select a product above to import its data.")
    End If

Answer 1

谢谢大家的帮助，我终于弄明白 "Object reference not set to an instance of an object." 实际上指的是@nick 所说的那行。

代码的问题是：

MySqlConn.ConnectionString = "Placeholder for pasting onto website" MySqlConn.Open() cmd.Connection = MySqlConn

我用 MySqlConn = New MySqlConnection

替换了该代码

MySqlConn.ConnectionString = "Placeholder for pasting onto website" Query = "INSERT INTO Cinema_Graph_Data (Rest of the giant query) cmd = New MySqlCommand(Query, MySqlConn) MySQLConn.Open() 位于所有参数的底部。 cmd 变量实际上根本没有初始化，因此成为对象引用错误的目标。感谢您告诉我有关调试的信息，并感谢您指出错误@Nick。

我现在唯一的问题是数据库无法翻译“£”符号而只显示“？”但我会尝试自己解决这个问题。再次感谢您的帮助！

SQL 插入多行，对象引用未设置为对象错误的实例

SQL inserting multiple lines, object reference not set to an instance of an object error

mysql

sql

.net

error-handling

object-reference