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Posted 12 Oct 2005


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Evaluate C# Code (Eval Function)

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4.74/5 (48 votes)
12 Oct 2005CPOL
An example that provides an Eval function for compiling/evaluating C# code at runtime.

Sample Image - EvalCSCode.jpg


This example shows an "Eval" function for C# and implements different usages of this evaluate function. The library is written in C# and can be tested with the MainForm in the solution.

Source view

Here you will see all the trick. The code generates a class structure with a basic "function prototype" in which the code to evaluate is filled in. The execution of the function should execute your code:

// Eval > Evaluates C# sourcelanguage
public static object Eval(string sCSCode) {

  CSharpCodeProvider c = new CSharpCodeProvider();
  ICodeCompiler icc = c.CreateCompiler();
  CompilerParameters cp = new CompilerParameters();


  cp.CompilerOptions = "/t:library";
  cp.GenerateInMemory = true;

  StringBuilder sb = new StringBuilder("");
  sb.Append("using System;\n" );
  sb.Append("using System.Xml;\n");
  sb.Append("using System.Data;\n");
  sb.Append("using System.Data.SqlClient;\n");
  sb.Append("using System.Windows.Forms;\n");
  sb.Append("using System.Drawing;\n");

  sb.Append("namespace CSCodeEvaler{ \n");
  sb.Append("public class CSCodeEvaler{ \n");
  sb.Append("public object EvalCode(){\n");
  sb.Append("return "+sCSCode+"; \n");
  sb.Append("} \n");
  sb.Append("} \n");

  CompilerResults cr = icc.CompileAssemblyFromSource(cp, sb.ToString());
  if( cr.Errors.Count > 0 ){
      MessageBox.Show("ERROR: " + cr.Errors[0].ErrorText, 
         "Error evaluating cs code", MessageBoxButtons.OK, 
         MessageBoxIcon.Error );
      return null;

  System.Reflection.Assembly a = cr.CompiledAssembly;
  object o = a.CreateInstance("CSCodeEvaler.CSCodeEvaler");

  Type t = o.GetType();
  MethodInfo mi = t.GetMethod("EvalCode");

  object s = mi.Invoke(o, null);
  return s;


Thanks fly out to:


  • Kim Hauser (dave) - Application Developer & System Engineer.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Software Developer (Senior)
Switzerland Switzerland
programmer and software junkie since 1991 zurich switzerland

Comments and Discussions

QuestionUseful. Pin
zamkinos14-Dec-18 23:56
Memberzamkinos14-Dec-18 23:56 
QuestionEval method in C#(Web API) like eval in javascript Pin
Member 1405901318-Nov-18 18:26
MemberMember 1405901318-Nov-18 18:26 
QuestionNot work Pin
Member 1178584723-Jun-15 2:30
MemberMember 1178584723-Jun-15 2:30 
QuestionExecuting code not in same class Namespace Pin
p3ptools23-Apr-15 8:33
Memberp3ptools23-Apr-15 8:33 
QuestionEval LINQ expersion Pin
FarazLoloei25-Oct-14 3:02
MemberFarazLoloei25-Oct-14 3:02 
QuestionGood work Pin
Sm.Abdullah6-Oct-12 20:13
MemberSm.Abdullah6-Oct-12 20:13 
QuestionHow do you replace a string at a given position with it's working code representative? Pin
Larissa Schön17-Mar-12 0:47
professionalLarissa Schön17-Mar-12 0:47 
GeneralAwesome, though quick question Pin
mbainrot10-Apr-09 21:03
Membermbainrot10-Apr-09 21:03 
QuestionEvalToObject Question Pin
gravelkm14-Nov-08 2:43
Membergravelkm14-Nov-08 2:43 
Questioncan a web project use "ReferencedAssemblies.Add("customer.dll")" Pin
wlbkeats7-Dec-06 23:34
Memberwlbkeats7-Dec-06 23:34 
AnswerRe: can a web project use "ReferencedAssemblies.Add("customer.dll")" Pin
lzuxiaolong27-Nov-12 15:13
Memberlzuxiaolong27-Nov-12 15:13 
GeneralUses of Eval Pin
Anup Shinde29-Sep-06 16:06
MemberAnup Shinde29-Sep-06 16:06 
GeneralTotal waste of time... Pin
markman@shaw.ca3-Mar-06 12:08
Membermarkman@shaw.ca3-Mar-06 12:08 
GeneralRe: Total waste of time... Pin
Pascal Ganaye20-Mar-06 9:12
MemberPascal Ganaye20-Mar-06 9:12 
GeneralRe: Total waste of time... Pin
markman@shaw.ca21-Mar-06 5:54
Membermarkman@shaw.ca21-Mar-06 5:54 
GeneralRe: Total waste of time... Pin
Graham Harrison11-Jan-07 23:34
MemberGraham Harrison11-Jan-07 23:34 
GeneralAn Eval Function for C# using JScript.NET (JavaScript) Pin
Michael Freidgeim5-Jan-11 0:48
MemberMichael Freidgeim5-Jan-11 0:48 
GeneralRe: Total waste of time... Pin
kim.david.hauser8-Feb-07 2:37
Memberkim.david.hauser8-Feb-07 2:37 
GeneralRe: Total waste of time... Pin
marketware30-Aug-07 11:25
Membermarketware30-Aug-07 11:25 
GeneralRe: Total waste of time... Pin
marketware31-Aug-07 11:08
Membermarketware31-Aug-07 11:08 
GeneralI dont think Total waste of time.. Pin
Midax27-Apr-10 9:40
MemberMidax27-Apr-10 9:40 
QuestionUses Pin
EvilToilet23-Oct-05 9:15
MemberEvilToilet23-Oct-05 9:15 
AnswerRe: Uses Pin
kim.david.hauser2-Nov-05 11:03
Memberkim.david.hauser2-Nov-05 11:03 
GeneralThanks for review... Pin
kim.david.hauser21-Oct-05 10:13
Memberkim.david.hauser21-Oct-05 10:13 
QuestionUsing a static method instead Pin
19-Oct-05 20:07
suss19-Oct-05 20:07 

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