Question

我在DataGridView控件中有几行。我想将每一行插入数据库。我试过这样的。但它给出了已添加参数的错误。如何添加一次参数名称，然后每次添加值并每次都执行它？

    Using connection As New SqlCeConnection(My.Settings.databaseConnectionString)
        Using command As New SqlCeCommand("INSERT INTO table_master(item, price) VALUES(@item, @price)", _
                                        connection)

            connection.Open()

            For Each r As DataGridViewRow In dgvMain.Rows
                If (Not String.IsNullOrWhiteSpace(r.Cells(1).Value)) Then
                    command.Parameters.AddWithValue("@item", r.Cells(1).Value.Trim)
                    command.Parameters.AddWithValue("@price", r.Cells(2).Value)


                    command.ExecuteNonQuery()
                End If
            Next

        End Using
    End Using

Answer 1

在循环外部和循环内部添加参数仅更新其值

Using connection As New SqlCeConnection(My.Settings.databaseConnectionString)
    Using command As New SqlCeCommand("INSERT INTO table_master(item, price) VALUES(@item, @price)", _
                                    connection)

        connection.Open()

        ' Create and add the parameters, just one time here with dummy values or'
        ' use the full syntax to create each single the parameter'
        command.Parameters.AddWithValue("@item", "")
        command.Parameters.AddWithValue("@price", 0)

        For Each r As DataGridViewRow In dgvMain.Rows
            If (Not String.IsNullOrWhiteSpace(r.Cells(1).Value)) Then

                command.Parameters("@item").Value = r.Cells(1).Value.Trim
                command.Parameters("@price").Value = r.Cells(2).Value
                command.ExecuteNonQuery()
            End If
        Next

    End Using
End Using

使用AddWithValue是一个很好的快捷方式，但有它的缺点。例如，不清楚列Price需要什么数据类型。使用Parameter构造函数，您可以指定参数的确切数据类型，并避免可能的转换错误

Dim p = new SqlCeParameter("@price", SqlDbType.Decimal)
command.Parameters.Add(p)
......

VB.Net插入多条记录

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