读取器关闭时无效尝试调用读取。 [英] Invalid attempt to call read when reader is closed.

问题描述

public void getdata（）

{





string str =select address，company from供应商，其中id = 1;







SqlDataReader dr = DB.ExecuteReader（str）; <如果（dr.Read（））

{
/>
txtAddress.Text = dr [address]。ToString（）;



txtCompany.Text = dr [company]。ToString（ ）;





dr.Close（）;





}

}

我发现此错误

读取器关闭时无效尝试调用Read。



我尝试过：



读取器关闭时无效尝试呼叫读取。

public void getdata()
{


string str = "select address,company from supplier where id=1";



SqlDataReader dr= DB.ExecuteReader(str);


if (dr.Read())
{

txtAddress.Text = dr["address"].ToString();

txtCompany.Text = dr["company"].ToString();


dr.Close();


}
}
and i find this error
Invalid attempt to call Read when reader is closed.

What I have tried:

Invalid attempt to call Read when reader is closed.

推荐答案

使用调试器查看错误发生的位置。

Use the debugger to see where the error occurs.

Quote：

读取器关闭时无效尝试调用Read。

Invalid attempt to call Read when reader is closed.

从错误消息中，您调用

From the error message, you call

dr.Read()

但是没有打开阅读器。





调试器允许你逐行跟踪执行，检查变量，你会发现它有一个点，它停止做你期望的。

调试器 - 维基百科，免费的百科全书 [ ^ ]

掌握Visual Studio 2010中的调试 - 初学者指南 [ ^ ]

but the reader is not opened.


The debugger allow you to follow the execution line by line, inspect variables and you will see that there is a point where it stop doing what you expect.
Debugger - Wikipedia, the free encyclopedia[^]
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]

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