如何使用C＃在Web服务中将文本写入txt文件？

Question

I have a web service.This service insert data to sql from some clients.I tried write inserted row and any Exception to a txt file.

void WriteLog(string Log)
{
    string FileName= "D:\\MyLogs.txt";
    StreamWriter obj;
    obj= new StreamWriter(FileName);
    obj.WriteLine(DateTime.Now.ToString() + " " + Log);
    obj.Close();
}

int row;
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["MyConn"].ConnectionString);

SqlCommand cmd = new SqlCommand();

[WebMethod]
public int InsertTable(int Age) {
    try {
        con.Open();
        cmd.CommandText=@"Insert into Table(Age) values(@Age)";
        cmd.Parameters.Add(new SqlParameter("Age", SqlDbType.Int, 32, "Age"));
        cmd.Parameters["Age"].Value = Age;
        cmd.Connection = con;
        cmd.ExecuteNonQuery();
        row = cmd.ExecuteNonQuery();

        WriteLog(row.ToString());    
    }
    catch (Exception ex) {
        WriteLog(ex.ToString());    
    }
    finally {
        con.Close();
        con.Dispose();
        cmd.Dispose();
    }
    return row;
}

I get this error : 'D:\\MyLogs.txt' Access to the path is denied.

Answer 1

You are getting a security exception since your asp.net running user does not have necessary rights to write to D: drive. Use following to get writable path in your application.

    private void WriteLog(string log)
    {
        string fileName= HttpContext.Current.Request.MapPath("MyLogs.txt");
        StreamWriter sw = new StreamWriter(fileName);
        sw.WriteLine(DateTime.Now.ToString() + " " + log);
        sw.Close();
    }

This method will give you a path where you are running (or deployed) your application. For example: you deployed your application to "c:\\inetpub\\www\\app1", then you will write to "c:\\inetpub\\www\\app1\\MyLogs.txt". It will change in your development machine according to wherever your project is.

Of course this method rewrite every log, therefore your MyLogs.txt contains only one log. Use following to append to your log file.

    private void WriteLog(string log)
    {
        string fileName= HttpContext.Current.Request.MapPath("MyLogs.txt");

        using (StreamWriter sw = File.AppendText(fileName)) 
        {
            sw.WriteLine(DateTime.Now.ToString() + " " + log);
        }   

    }

Of course you can give your running user necessary rights to "D: drive" but I recommend against it. Your application should run without additional privileges.

Answer 2

You need to make sure the credential that the thread is running with has access to the file. Try giving IUSR to have read-write-execute permissions for the file.