1.compile File.cs and generate  File.exe编译file.cs 生成file.exe
    csc file.cs
2.comple File.cs and generate File.dll编译file.cs生成file.dll
    csc /target:library filel.cs
3.only complie file.cs without generating any output只生成file.cs不生成其他文件
   csc /nooutput file.cs
4.compile file.cs and generate my.exe编译file.cs生成my.exe文件
    csc /out:my.exe file.cs
5. compile file.cs by refering to some.dll通过引用some.dll编译file.cs(适用于file.cs用到的namespace在some.dll里面定义）
     csc /r:some.dll File.cs