什么导致asp.net内存溢出异常

I have a simple asp.net website which reads a large text file into memory and does some processing. Below is the code that raises OOM exception. After reading about 350k lines, I get this error. Each line has an average of 1k characters. Is there some memory limit with IIS or ASP.Net websites? My server still has plenty of physical memory left. Thanks.I have a simple asp.net website which reads a l