What is the proper way to write larger (50mb) bytes to file in c sharp

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C#

WPF

FileIO

Hi All,
I want to write larger (50mb)bytes to file for download log purpose in my application. I am getting out of memory exception some time. To avoid Out of memory exception i googled and find the below code.

using (StringReader file = new StringReader(result))
               {
                   var line = file.ReadLine();
                   while (line != null)
                   {
                       if (cancelLog)
                       {
                           GC.Collect();
                           return;
                       }
                       File.AppendAllText(fileName, line + Environment.NewLine, new UTF8Encoding());
                       line = file.ReadLine();
                   }
               }

But it takes long time to write the file. Can anyone please tell me the proper way to avoid out of memory exception in larger file situation.

Thanks in advance.