请帮助-添加记录女士访问权限 [英] Please Help - Add Record Ms Access

问题描述

嗨
我在表单上有10个文本框，允许用户填写并添加到msaccess数据库中.但我收到以下行中的错误未将对象引用设置为对象的实例.-未处理NullReferenceExcption". cmd.Connection = con-请您帮忙解决造成此问题的原因?

Hi
I have 10 textbox on a form that allow user to fill in and adds to the msaccess database. but i am recieving an error " Object reference not set to an instance of an object. - NullReferenceExcption Was Unhandled" at the following line
cmd.Connection = con - Please could you help with what is causing this issue?

 Dim con As New OleDb.OleDbConnection
        Dim cmd As OleDb.OleDbCommand
        Dim eep As New String("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\FHand\Db\FedUp.mdb")
        con.ConnectionString = eep

        If con.State = ConnectionState.Open Then
            con.Open()
        End If

        ''Add To Table
        cmd.Connection = con
        cmd.CommandText = "INSERT INTO Field_Yard(ID, Field_ID, Field_Name, Field_Title, Field_Description, Field_Type, Field_Spec, CON_Nodeid, Field_Lenght, Field_Width)" & _
" VALUES (" & Me.txtid.Text & ",''" & Me.txtFID.Text & "'',''" & Me.txtfname.Text & "'',''" & Me.txtftitle.Text & "'',''" & Me.txtfdescription.Text & "'',''" & Me.txtftype.Text & "'',''" & Me.txtfspec.Text & "'',''" & Me.txtconnode.Text & "'',''" & Me.TXTlenght.Text & "'',''" & Me.txtWidth.Text & "'')"
        cmd.ExecuteNonQuery()

        con.Close()

    End Sub

推荐答案

我认为您的问题是命令对象.

你有这个:

I think your problem is that the command object.

You have this:

Dim cmd As OleDb.OleDbCommand

但是您需要该对象的新实例，因此请尝试以下操作:

But you need a new instance of the object, so try this instead:

Dim cmd As New OleDb.OleDbCommand

希望对您有所帮助.

Hope this helps.

对VB不太了解，但乍一看我认为问题出在这里:-

Don''t know much of VB but at 1st look i think problem is here:-

If con.State = ConnectionState.Open Then
            con.Open()

我想检查是否需要使用相等性(==)，如果连接已经打开，则需要再次打开它

所以尝试这样的事情:-

I suppose to check equality you need to use (==)and if connection is already open what''s the need of opening it again

so try something like this:-

If con.State==ConnectionState.Closed Then
con.Open()

祝您好运；

Best of luck;

使用以下代码结构在访问数据库中添加值

Use following code structure to add values in access database

'Creating Connection object
Public con As New OleDb.OleDbConnection
'Creating data adapter object
Public objda As New OleDb.OleDbDataAdapter
If con.State = ConnectionState.Open Then       'Checking Connection State
con.Close()                                    'Closing Connection
End If
con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Application.StartupPath & "\DatabaseName.mdb"
Try
con.Open()                                     'Opening Connection
Catch ex As Exception                  'Providing Error Message
MessageBox.Show("Please Contact Application Developer", "Database Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End                                            'Closing Application
End Try
objda.SelectCommand = New OleDbCommand
objda.SelectCommand.CommandText = "Insert into TableName(Field1, Field2) values(@Field1, @Field2)"
objda.SelectCommand.Parameters.AddWithValue("@Field1", Textbox1.Text)
objda.SelectCommand.Parameters.AddWithValue("@Field2",Textbox2.Text) 
'Assigning value of TextField to variable @Eid
Try                                         'To handle OleDb Exceptions
objda.SelectCommand.ExecuteNonQuery()
Catch ex As OleDb.OleDbException
MessageBox.Show(ex.Message)
End Try

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