NullReferenceException：未将对象引用设置为对象的实例 [英] NullReferenceException: Object reference not set to an instance of an object

问题描述

public DataTable GetListRegionMaster()
{
 try
 {
    DataTable dt = new DataTable();
    SqlCommand cmd = new SqlCommand("spListReligion");
    cmd.CommandType = CommandType.StoredProcedure;
    dt = dbobj.ExecuteDTQuery(cmd);
    return dt;
  }
  catch (Exception ex)
  {
     throw ex;
  }
  finally
  { dbobj = null; }
  }

存储过程：

Store Procedure :

ALTER PROCEDURE [dbo].[spListReligion]
AS
BEGIN

    SELECT * FROM dbo.Religion ORDER BY ReligionName

END

给出NullReferenceException：对象引用未设置为对象的实例

Plz帮我Boss



/编辑代码块由Jibesh / Edit

giving NullReferenceException: Object reference not set to an instance of an object
Plz help me Boss

/Edit Code Block Added by Jibesh /Edit

推荐答案

尝试调试源代码以找出问题。



似乎 dbobj 为空，当您对此执行查询时，会出现错误。

Try debugging your source code to figure out the problem.

It appears that dbobj is null and when you execute on a query on this, you get the error.

你没有显示异常wi的位置抛出对象引用未设置为对象的实例的消息，但这是最容易检测和修复的情况之一。它只是意味着某些引用类型的某个成员/变量通过使用和它的实例（非静态）成员解除引用，这要求此成员/变量为非null，但实际上它似乎为null。只需在调试器下执行它，它将停止抛出异常的执行。在该行上设置一个断点，重新启动应用程序并再次到达这一点。评估下一行中涉及的所有引用，并查看哪一个为null，而不需要为null。解决这个问题之后，修复代码：确保将成员/变量正确初始化为非空引用，或者将其检查为null，如果为null，则执行其他操作。



另见我过去的答案：想要在点击按钮时显示下一条记录。但得到了在如果下一个记录功能的病症对象引用不设置为一个对象的一个​​实例 [ ^ ]。

-SA

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown, but this is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: wither make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.

See also my past answer: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object"[^].

—SA

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