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Evaluate C# Code (Eval Function)

, 12 Oct 2005
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An example that provides an Eval function for compiling/evaluating C# code at runtime.

Sample Image - EvalCSCode.jpg

Introduction

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.ReferencedAssemblies.Add("system.dll");
  cp.ReferencedAssemblies.Add("system.xml.dll");
  cp.ReferencedAssemblies.Add("system.data.dll");
  cp.ReferencedAssemblies.Add("system.windows.forms.dll");
  cp.ReferencedAssemblies.Add("system.drawing.dll");

  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");
  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:

Credits:

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

License

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

About the Author

kim.david.hauser
Software Developer (Senior)
Switzerland Switzerland
programmer and software junkie since 1991 zurich switzerland
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Comments and Discussions

 
QuestionGood work PinmemberSm.Abdullah6-Oct-12 20:13 
QuestionHow do you replace a string at a given position with it's working code representative? PinmemberLarissa Schön17-Mar-12 0:47 
GeneralAwesome, though quick question Pinmembermbainrot10-Apr-09 21:03 
QuestionEvalToObject Question Pinmembergravelkm14-Nov-08 2:43 
Questioncan a web project use "ReferencedAssemblies.Add("customer.dll")" Pinmemberwlbkeats7-Dec-06 23:34 
AnswerRe: can a web project use "ReferencedAssemblies.Add("customer.dll")" Pinmemberlzuxiaolong27-Nov-12 15:13 
GeneralUses of Eval PinmemberAnup Shinde29-Sep-06 16:06 
GeneralTotal waste of time... Pinmembermarkman@shaw.ca3-Mar-06 12:08 
Way too slow to compile on the fly! Eval.JScriptEvaluate is so much better. Too bad it has been obsoleted in .NET 2.0.
GeneralRe: Total waste of time... PinmemberPascal Ganaye20-Mar-06 9:12 
GeneralRe: Total waste of time... Pinmembermarkman@shaw.ca21-Mar-06 5:54 
GeneralRe: Total waste of time... PinmemberGraham Harrison11-Jan-07 23:34 
GeneralAn Eval Function for C# using JScript.NET (JavaScript) PinmemberMichael Freidgeim5-Jan-11 0:48 
GeneralRe: Total waste of time... Pinmemberkim.hauser8-Feb-07 2:37 
GeneralRe: Total waste of time... Pinmembermarketware30-Aug-07 11:25 
GeneralRe: Total waste of time... Pinmembermarketware31-Aug-07 11:08 
GeneralI dont think Total waste of time.. PinmemberMidax27-Apr-10 9:40 
QuestionUses PinmemberEvilToilet23-Oct-05 9:15 
AnswerRe: Uses Pinmemberkim.hauser2-Nov-05 11:03 
GeneralThanks for review... Pinmemberkim.hauser21-Oct-05 10:13 
QuestionUsing a static method instead Pinmemberanonymous19-Oct-05 20:07 
AnswerRe: Using a static method instead Pinmemberaprenot21-Oct-05 10:17 
GeneralRe: Using a static method instead PinmemberToli Cuturicu20-Dec-10 11:22 
GeneralExcellent! But Pinmembercccccbbbbb19-Oct-05 14:41 
GeneralRe: Excellent! But Pinmemberkim.hauser22-Oct-05 0:29 
AnswerRe: Excellent! But PinmemberKevan Davis1-Dec-06 11:18 
GeneralExcellent !! PinmemberTittle Joseph18-Oct-05 19:46 
GeneralThanks, but ... PinmemberHerman Chelette18-Oct-05 2:33 
GeneralRe: Thanks, but ... Pinmemberkim.hauser21-Oct-05 9:34 
GeneralGreat Job Pinmemberaprenot13-Oct-05 5:02 
GeneralRe: Great Job PinsussAnonymous21-Oct-05 9:52 

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