vb.net – SqlCommand(使用Statement / Disposing问题)

Using cn As New SqlConnection(ConnectionString)
            Try
                Dim cmd As SqlCommand = New SqlCommand
                With cmd
                    .Connection = cn
                    .Connection.Open()
                    .CommandText = "dbo.GetCustomerByID"
                    .CommandType = CommandType.StoredProcedure
                    .Parameters.Add("@CustomerID",SqlDbType.Int,4)
                    .Parameters("@CustomerID").Value = CustomerID
                End With

                da = New SqlDataAdapter(cmd)
                da.Fill(ds,"Customer")
            Catch ex As Exception

            End Try
        End Using

根据我今天的研究,听起来好像这基本上还可以,但是SqlCommand没有被处理掉.

问题 – >以下哪个例子是处理这个问题的最佳方法？

示例2 – 手动处理

Using cn As New SqlConnection(ConnectionString)
            Try
                Dim cmd As SqlCommand = New SqlCommand
                With cmd
                    .Connection = cn
                    .Connection.Open()
                    .CommandText = "dbo.GetCustomerByID"
                    .CommandType = CommandType.StoredProcedure
                    .Parameters.Add("@CustomerID",4)
                    .Parameters("@CustomerID").Value = CustomerID
                End With

                da = New SqlDataAdapter(cmd)
                cmd.Dispose()
                da.Fill(ds,"Customer")
            Catch ex As Exception

            End Try
        End Using

示例3 – 使用Using语句自动处理

Using cn As New SqlConnection(ConnectionString)
            Try
                Using cmd As New SqlCommand
                    With cmd
                        .Connection = cn
                        .Connection.Open()
                        .CommandText = "dbo.GetCustomerByID"
                        .CommandType = CommandType.StoredProcedure
                        .Parameters.Add("@CustomerID",4)
                        .Parameters("@CustomerID").Value = CustomerID
                    End With

                    da = New SqlDataAdapter(cmd)
                    da.Fill(ds,"Customer")
                End Using
            Catch ex As Exception

            End Try
        End Using

示例4 – 与示例3相同,但Try / Catch在使用中 – 这是否有所不同？

Using cn As New SqlConnection(ConnectionString)
            Using cmd As New SqlCommand
                Try
                    With cmd
                        .Connection = cn
                        .Connection.Open()
                        .CommandText = "dbo.GetCustomerByID"
                        .CommandType = CommandType.StoredProcedure
                        .Parameters.Add("@CustomerID","Customer")
                Catch ex As Exception

                End Try
            End Using
        End Using

示例5 – 与示例4相同,但CommandText和cn在Using语句中指定 – 这有什么优势？

Using cn As New SqlConnection(ConnectionString)
            Using cmd As New SqlCommand("GetCustomerByID",cn)
                Try
                    With cmd
                        .Connection.Open()
                        .CommandType = CommandType.StoredProcedure
                        .Parameters.Add("@CustomerID","Customer")
                Catch ex As Exception

                End Try
            End Using
        End Using

示例6 – 与示例5相同,但是在cn而不是cmd上打开连接.如果只执行一个存储过程,是否最好在cmd上打开连接？

Using cn As New SqlConnection(ConnectionString)
            cn.Open()

            Using cmd As New SqlCommand("GetCustomerByID",cn)
                Try
                    With cmd
                        .Connection = cn
                        .CommandType = CommandType.StoredProcedure
                        .Parameters.Add("@CustomerID","Customer")
                Catch ex As Exception

                End Try
            End Using
        End Using