What is the Difference between System.IO.File.OpenRead AND System.IO.FileStream?

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C#

.NET

Hello all,
n my application i am reading .PDF file useing System.IO.FileStream (filePath). This is working fine when folder have local user right. When i remove Local user right from folder that time this gives access denied error. I am use this code...

System.IO.FileStream objFStream = new System.IO.FileStream(strPath, System.IO.FileMode.Open);
        byte[] bytRead = new byte[(int)objFStream.Length];
        objFStream.Read(bytRead, 0, (int)objFStream.Length);
        objFStream.Close();
        objFStream.Dispose();

Once i replace System.IO.FileStream to System.IO.File.OpenRead(strPath) it will work. Replace code is..

System.IO.FileStream objFStream = System.IO.File.OpenRead(strPath);
            byte[] bytRead = new byte[(int)objFStream.Length];
            objFStream.Read(bytRead, 0, (int)objFStream.Length);
            objFStream.Close();
            objFStream.Dispose();

I want to know what is the different between this?
If any one know please help.