VB.NET SQL Server插入-ExecuteNonQuery：连接属性尚未初始化

问题描述

|| 在表单加载事件中，我连接到SQL Server数据库：

Private Sub AddBook_Load(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles MyBase.Load
            myConnection = New SqlConnection(\"server=.\\SQLEXPRESS;uid=sa;pwd=123;database=CIEDC\")
            myConnection.Open()

End Sub

在Insert事件中，我使用以下代码：

Private Sub cmdAdd_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles cmdAdd.Click
            Try
                myConnection.Open()
                myCommand = New SqlCommand(\"INSERT INTO tblBook(BookCode,BookTitle,Author,PublishingYear,Price,EnterDate,CatID,RackID,Amount) VALUES(\'\" & txtBookCode.Text & \"\',\'\" & txtTitle.Text & \"\',\'\" & txtAuthor.Text & \"\',\'\" & txtPublishYear.Text & \"\',\'\" & txtPrice.Text & \"\',#\" & txtEnterDate.Text & \"#,\" & txtCategory.Text & \",\" & txtRack.Text & \",\" & txtAmount.Text & \")\")
                myCommand.ExecuteNonQuery()
                MsgBox(\"The book named \'\" & txtTitle.Text & \"\' has been inseted successfully\")
                ClearBox()
            Catch ex As Exception
                MsgBox(ex.Message())
            End Try
            myConnection.Close()
End Sub

并且它产生以下错误：

ExecuteNonQuery: Connection property has not been initialized

    

解决方法

         连接分配-您未设置SQLCommand的连接属性。您无需添加任何代码即可执行此操作。这是导致您出错的原因。

myCommand = New SqlCommand(\"INSERT INTO tblBook(BookCode,BookTitle,Author,PublishingYear,Price,EnterDate,CatID,RackID,Amount) VALUES(\'\" & txtBookCode.Text & \"\',\'\" & txtTitle.Text & \"\',\'\" & txtAuthor.Text & \"\',\'\" & txtPublishYear.Text & \"\',\'\" & txtPrice.Text & \"\',#\" & txtEnterDate.Text & \"#,\" & txtCategory.Text & \",\" & txtRack.Text & \",\" & txtAmount.Text & \")\",MyConnection)

连接处理-您还需要从负载处理程序中删除“ MyConnection.Open \”。只需打开它，然后像现在一样在您的Click Handler中将其关闭即可。这不会导致错误。 参数化SQL-尽管您没有使用存储过程，但仍需要使用SQL参数。这不是您的错误的原因。正如Conrad提醒我的那样，您的原始代码将用户的值直接转储到SQL语句中。除非您使用SQL参数，否则恶意用户将窃取您的数据。

Dim CMD As New SqlCommand(\"Select * from MyTable where BookID = @BookID\")
CMD.Parameters.Add(\"@BookID\",SqlDbType.Int).Value = CInt(TXT_BookdID.Text)

    ,        您需要在命令上设置

Connection

属性：

myCommand.Connection = myConnection

    ,        错误消息所暗示的几乎是-尚未将SqlCommand对象的Connection属性分配给您打开的连接（在本例中，您将其称为“ 7”）。 另外，这里有个建议。对sql参数进行一些阅读-在没有任何健全性检查的情况下从用户输入进行sql连接是SQL注入攻击发生的方式。 这是一种方法：

Private Sub cmdAdd_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles cmdAdd.Click
    Try
        myConnection.Open()
        myCommand = New SqlCommand( _
        \"INSERT INTO tblBook(BookCode,\" & _
        \"                    EnterDate,Amount) \" & _
        \"VALUES(@bookCode,@bookTitle,@author,@publishingYear,@price,@enterDate,\" & _
        \"       @catId,@rackId,@amount)\")
        myCommand.Connection = myConnection
        with myCommand.Parameters
            .AddWithValue(\"bookCode\",txtBookCode.Text)
            .AddWithValue(\"bookTitle\",txtTitle.Text)
            .AddWithValue(\"author\",txtAuthor.Text)
            .AddWithValue(\"publishingYear\",txtPublishYear.Text)
            .AddWithValue(\"price\",txtPrice.Text)
            .AddWithValue(\"enterDate\",txtEnterDate.Text)
            .AddWithValue(\"catId\",txtCategory.Text)
            .AddWithValue(\"rackId\",txtRack.Text)
            .AddWithValue(\"amount\",txtAmount.Text)
        end with
        myCommand.ExecuteNonQuery()
        MsgBox(\"The book named \'\" & txtTitle.Text & \"\' has been inseted successfully\")
        ClearBox()
    Catch ex As Exception
        MsgBox(ex.Message())
    End Try
    myConnection.Close()
End Sub

    ,        模块Module1     公共con作为System.Data.SqlClient.SqlConnection     公共com作为System.Data.SqlClient.SqlCommand     公共ds作为System.Data.SqlClient.SqlDataReader     昏暗的sqlstr作为字符串

Public Sub main()
    con = New SqlConnection(\"Data Source=.....;Initial Catalog=.....;Integrated Security=True;\")
    con.Open()
    frmopen.Show()
    \'sqlstr = \"select * from name1\"
    \'com = New SqlCommand(sqlstr,con)
    Try
        com.ExecuteNonQuery()

        \'MsgBox(\"success\",MsgBoxStyle.Information)
    Catch ex As Exception
        MsgBox(ex.Message())
    End Try
    \'con.Close()



    \'MsgBox(\"ok\",MsgBoxStyle.Information,)

End Sub

终端模块     ,        请尝试将使用的连接（包括仅打开）包装在USING块内。假设使用web.config作为连接字符串：

    Dim connection As New SqlConnection(ConfigurationManager.ConnectionStrings(\"web.config_connectionstring\").ConnectionString)
    Dim query As New String = \"select * from Table1\"
    Dim command as New SqlCommand(query,connection)

Using connection
   connection.Open()
   command.ExecuteNonQuery()
End Using

并请用户输入任何参数。