如何插入NULL到数据库中，如果表单字段使用ASP.NET和放大器是空的; VB [英] How to insert NULL into database if form field is empty using ASP.NET & VB

问题描述

我有一个从形式插入数据的格式，并存储过程。它工作正常，但如果一个字段没有填写不插入 NULL 到SQL它插入，。

I have a form and stored procedure that inserts the data from the form. It works fine except that if a field isn't filled in it doesn't insert a NULL into SQL it inserts "".

我已经尝试了几种不同的方法，但似乎没有要插入 NULL ，下面还是插入一个，，任何人都可以点我在正确的方向？

I've tried a few different ways but none seem to insert NULL, the one below still inserts "", can anyone point me in the right direction?

下面是code的必需部分，如果你需要更多的只是让我知道。

Here is the required part of the code, if you require more just let me know.

Dim rdr As SqlDataReader
            Dim cmdInsert As SqlCommand = New SqlCommand()
            cmdInsert.CommandText = "spPersonalDetailsInsert"
            cmdInsert.CommandType = CommandType.StoredProcedure
            cmdInsert.Connection = connSQL


            Dim firstname, lastname, address, address1, town, county, postcode As SqlParameter
            'convert to null if ""
            Dim frmFirstName As String
            If pd_first_name.Text = "" Then
                frmFirstName = Convert.DBNull
            Else
                frmFirstName = pd_first_name.Text
            End If

            firstname = New SqlParameter()
            firstname.ParameterName = "@firstname"
            firstname.SqlDbType = SqlDbType.NVarChar
            firstname.Size = 50
            firstname.Direction = ParameterDirection.Input
            firstname.Value = frmFirstName

修改

我测试了以下code：

I tested the following code:

If pd_first_name.Text = "" Then
            frmFirstName = DBNull.Value
        Else
            frmFirstName = pd_first_name.Text
        End If

但它仍然不会插入 NULL 所以我测试的：

            If pd_first_name.Text = "" Then
                Response.Write("NULL")
                address1.Value = DBNull.Value
            Else
                Response.Write("NOT NULL")
                address1.Value = pd_address1.Text
            End If

所以，如果我输入什么到地址1 字段应该写 NULL 屏幕，但它始终写入 NOT NULL 。这是什么一个空的表单字段平等的吗？在传统的ASP它总是，。

So if I enter nothing into address1 field it should write NULL to screen but it always writes NOT NULL. What does an empty form field equal? in classic ASP it was always "".

推荐答案

您需要使用的 DBNull.Value

            If String.IsNullOrEmpty(pd_first_name.Text.ToString().Trim) = true Then
                frmFirstName = DBNull.Value
            Else
                frmFirstName = pd_first_name.Text
            End If

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