Reflection application-compile a string to obtain the computing result

1 using System;
2 using System. Data;
3 using System. Configuration;
4 using System. Collections;
5 using System. Web;
6 using System. Web. Security;
7 using System. Web. UI;
8 using System. Web. UI. WebControls;
9 using System. Web. UI. WebControls. WebParts;
10 using System. Web. UI. HtmlControls;
11 using System. Text;
12 using System. CodeDom. Compiler;
13 using Microsoft. CSharp;
14 using System. Reflection;
15
16 public partial class Default2: System. Web. UI. Page
17 {
18 protected void Page_Load (object sender, EventArgs e)
19 {
20 TimeSpan Ts = new TimeSpan ();
21 DateTime dtStar = DateTime. Now;
22 Evaluator ev = new Evaluator ();
23 Response. Write (ev. Eval ("2*2*3*10*3.12/811 "));
24 DateTime dtEnd = DateTime. Now;
25 Ts = dtEnd-dtStar;
26 Response. Write ("<br>" + Ts. TotalMilliseconds. ToString ());
27}
28}
29 public class Evaluator
30 {
31 private static CodeDomProvider comp = new CSharpCodeProvider ();
32 private static CompilerParameters cp = new CompilerParameters ();
33 private static MethodInfo mi;
34 public object Eval (string expression)
35 {
36 StringBuilder codeBuilder = new StringBuilder ();
37 codeBuilder. Append ("using System ;");
38 codeBuilder. Append ("using Microsoft. CSharp ;");
39 codeBuilder. Append ("");
40 codeBuilder. Append ("public class Mode ");
41 codeBuilder. Append ("{");
42 codeBuilder. Append ("public static object Func ()");
43 codeBuilder. Append ("{");
44 codeBuilder. Append ("return" + expression + ";");
45 codeBuilder. Append ("}");
46 codeBuilder. Append ("}");
47 cp. ReferencedAssemblies. Add ("System. dll ");
48 cp. GenerateExecutable = false;
49 cp. GenerateInMemory = true;
50 string code = codeBuilder. ToString ();
51 string [] stra = new string [] {code };
52 CompilerResults cr = comp. CreateCompiler (). CompileAssemblyFromSource (cp, code );
53 if (cr. Errors. HasErrors)
54 {
55 return null;
56}
57 else
58 {
59 Assembly a = cr. CompiledAssembly;
60 Type t = a. GetType ("Mode ");
61 mi = t. GetMethod ("Func", BindingFlags. Static | BindingFlags. Public );
62 return mi. Invoke (null, new object [0]);
63}
64}
65}