在我的项目中我有两个不同名称的表单我打开了两个连接Sql Server在此代码中出错 [英] In My Project I Am Having Two Forms With Different Names I Opened Two Connections For Sql Server Getting Error In This Code

问题描述

我的第一个表单代码正常工作

  Dim  SCON 作为 字符串 =  数据源= localhost; database = Medha_call; user id = sa; password = user 

这是我的第二个得到错误的NullReferenceExceptionHandling按用户代码

 con.ConnectionString = SCON 
  Dim  conn2  As  字符串 =  数据源= localhost;初始目录= Medha_call;用户ID = sa;密码=用户 
 con.ConnectionString = conn2 

请帮我解释代码和错误详情？



感谢你...

解决方案

很可能你没有初始化 con var iable。



在使用y变量之前你应该在某个地方有一个代码行，比如

  Dim  con  As  SqlConnection = 新 SqlConnection 
 ... 

但是，我更喜欢使用Use作为连接，如 SqlConnection [ ^ ]

 使用连接作为 新 SqlConnection（ connectionString）
 '  ...通过连接做一些事情......  
 结束 使用 

my first form code is working properly

Dim SCON As String = "data source=localhost;database=Medha_call;user id=sa;password=user"

this my second one getting error as NullReferenceExceptionHandling By user code

con.ConnectionString = SCON
Dim conn2 As String = "Data Source=localhost;Initial Catalog=Medha_call;User ID=sa;Password=user"
con.ConnectionString = conn2

please help me the code and the error details?

thanking you...

解决方案

Most likely you haven't initialized the con variable.

Before using yhe con variable you should somewhere have a code line like

Dim con As SqlConnection = New SqlConnection
... 

However, I'd prefer to use Using for the connection as in the example in SqlConnection[^]

Using connection As New SqlConnection(connectionString)
'... do somethig with the connection...
End Using

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