Is there a way to calculate the result of a string expression, for example
mystring = "2*a+32-Math.Sin(6)" dynamically knowing that a is a variable that I have, may be there is some dynamic solution or using System.Reflection
string mystring = "2*a+32-Math.Sin(6)"`;
decimal result = SomeMethod(mystring,3); // where a = 3 for example
How about making javascript calculate your expression?
Type scriptType = Type.GetTypeFromCLSID(Guid.Parse("0E59F1D5-1FBE-11D0-8FF2-00A0D10038BC"));
dynamic obj = Activator.CreateInstance(scriptType, false);
obj.Language = "javascript";
var res = obj.Eval("a=3; 2*a+32-Math.sin(6)");
You can use Compute methood of Datatable in SomeMethod in following way:
static decimal Somemethod(int val)
{
var result = (decimal)new DataTable().Compute(string.Format("2*{0}+32-{1}", val, Math.Sin(6)), "");
return result;
}
Simply, you can call like this:
result = Somemethod(3);
if found this its working perfectly, sorry for the bother, all I wanted is on the fly compiler. & this what i get
MessageBox.Show(Eval("5*3-Math.Sin(12) + 25*Math.Pow(3,2)").ToString());
public static object Eval(string sCSCode)
{
CodeDomProvider icc = CodeDomProvider.CreateProvider("C#");
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", MessageBoxButton.OK,
MessageBoxImage.Error);
return null;
}
System.Reflection.Assembly a = cr.CompiledAssembly;
object o = a.CreateInstance("CSCodeEvaler.CSCodeEvaler");
Type t = o.GetType();
System.Reflection.MethodInfo mi = t.GetMethod("EvalCode");
object s = mi.Invoke(o, null);
return s;
}
Here are some of the most popular approaches that I am aware of for evaluating string expressions dynamically in C#.
I don't think there's any native support for what you are asking, however there are a number of ways to accomplish it, none of which are totally trivial but in the order that I think they are easy:
leverage an embedded language with the expression support you desire. For example iron ruby: http://ironruby.codeplex.com/
use the C# compiler from your program as in How does LINQPad compile code?.
write your own parse with something like irony: http://irony.codeplex.com/
Once parsed you could use expression trees to get your result: http://msdn.microsoft.com/en-us/library/bb397951.aspx
Make abstract class With the methods you want to use to evaluate the expressions. In run time make a new class that inherits that one. I will share the code soon.
as promised here is the code to do it:
public class BaseClass
{
public BaseClass(){}
public virtual double Eval(double x,double y){return 0;}
}
public class MathExpressionParser
{
private BaseClass Evalulator=null;
public MathExpressionParser(){}
public bool Intialize(string equation)
{
Microsoft.CSharp.CSharpCodeProvider cp=new Microsoft.CSharp.CSharpCodeProvider();
System.CodeDom.Compiler.ICodeCompiler comp=cp.CreateCompiler();
System.CodeDom.Compiler.CompilerParameters cpar=new CompilerParameters();
cpar.GenerateInMemory=true;
cpar.GenerateExecutable=false;
cpar.ReferencedAssemblies.Add("system.dll");
cpar.ReferencedAssemblies.Add("EquationsParser.exe"); //Did you see this before;
string sourceCode="using System;"+
"class DrivedEval:EquationsParser.BaseClass" +
"{"+
"public DrivedEval(){}"+
"public override double Eval(double x,double y)"+
"{"+
"return "+ /*Looook here code insertion*/ equation +";"+
"}"+
"}";
//the previouse source code will be compiled now(run time);
CompilerResults result=comp.CompileAssemblyFromSource(cpar,sourceCode);
//If there are error in the code display it for the programmer who enter the equation
string errors="";
foreach(CompilerError rrr in result.Errors)
{
if(rrr.IsWarning)
continue;
errors+="\n"+rrr.ErrorText;
errors+="\n"+rrr.ToString();
}
//You Can show error if there in the sourceCode you just compiled uncomment the following
//MessageBox.Show(errors);
if(result.Errors.Count==0&&result.CompiledAssembly!=null)
{
Type objtype=result.CompiledAssembly.GetType("DrivedEval");
try
{
if(objtype!=null)
{
Evalulator=(BaseClass)Activator.CreateInstance(objtype);
}
}
catch(Exception ex)
{
MessageBox.Show(ex.Message,"Error in Creation the object");
}
return true;
}
else return false;
}
public double evaluate(double x,double y)
{
if(Evalulator==null)
return 0.0;
return this.Evalulator.Eval(x,y);
}
}
and you will need to do the following simple test to make sure it works:
private void button1_Click(object sender, System.EventArgs e)
{
if(parser.Intialize(textBox1.Text)==false)
{
MessageBox.Show("Check equation");
return;
}
textBox4.Text=(parser.evaluate(double.Parse(textBox2.Text),double.Parse(textBox3.Text))).ToString();
}
