如何处理以下代码的异常 [英] How to handle exception of following code

问题描述

我有以下代码

I have following code

try
            {
                SqlCommand OpenCat = new SqlCommand(SQL, MainClass.Conn);
                SqlDataReader readCat = OpenCat.ExecuteReader();
                if (readCat.Read())
                {
                    cmbPettyCashCode.Text = MainClass.SetDefo(readCat.GetValue(0).ToString(), "");
                    txtCatName.Text = MainClass.SetDefo(readCat.GetValue(1).ToString(), "");
                    readCat.Dispose();
                }
                else
                {
                    readCat.Dispose();
                }
               
            }
            catch (Exception error)
            {
                
                cmbPettyCashCode.Text = "";
                MessageBox.Show(error.Message.ToString(), "Message", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            }
            finally {  }

我看不到OpenCat和readCat在捕获点如何处理这个



谢谢

I Can't See "OpenCat" and "readCat" at the catch point how to handle this

thanks

推荐答案

最佳实践正在使用使用BLOCK如下所示，它将在发生异常时处理连接/命令/阅读器

best practice is using "USING BLOCK" as below, it will dispose the connection/command/ reader even when exception occurred

using(SqlConnection connection = ...)
{
    connection.Open();
    ...
    using(SqlCommand command = ...)
    {
        using(SqlDataReader reader = command.ExecuteReader())
        {
            ... do your stuff ...
        } // reader is closed/disposed here
    } // command is closed/disposed here
} // connection is closed/disposed here

参考理解C＃中的使用语句 [ ^ ]

和 SQLDataReader dispose？ [ ^ ]

如果要在catch和/或finally块中访问它们，则需要在try块之外声明变量。



由于@DamithSL已经回答，请使用使用语句确保您的连接将在最后处理，是否发生异常。



您仍然可以使用中编写 try / catch 块c $ c>阻止，这样你的 catch 块可以专注于错误处理：将异常详细信息写入日志文件并向用户显示错误消息。

You will need to declare your variables outside of the try block if you want to access them in the catch and/or finally block.

As @DamithSL already answered, use using statement to make sure your connection will be disposed at the end, whether an exception occurs or not.

You can still write your try/catch blocks within the using block and this way your catch block can focus on error handling: write exception details to log file and display error message to user.

SqlCommand OpenCat = new SqlCommand(SQL, MainClass.Conn);
SqlDataReader readCat = new SqlDataReader();
try
{
readCat = OpenCat.ExecuteReader();
if (readCat.Read())
{
cmbPettyCashCode.Text = MainClass.SetDefo(readCat.GetValue(0).ToString(), "");
txtCatName.Text = MainClass.SetDefo(readCat.GetValue(1).ToString(), "");
readCat.Dispose();
}
else
{
readCat.Dispose();
} 
}
catch (Exception error)
{
//access your variables here, as they are now global 
cmbPettyCashCode.Text = "";
MessageBox.Show(error.Message.ToString(), "Message", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
finally { }

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