Special Characters in String

If I understand correctly, you are able to extract character (+, * etc) from a string.

But Your char.IsSymbol returns true only for + symbol and not for others.

This is expected behaviour as IsSymbol works little strangely. It returns true only if character belonngs to one of the following Unicode categories. MathSymbol, CurrencySymbol, ModifierSymbol, and OtherSymbol.

And guess what, * , - doesn't fall in any of this category. Check yourself with following code

Console.WriteLine(Char.GetUnicodeCategory('*').ToString());

Console.WriteLine(Char.GetUnicodeCategory('-').ToString());

The best way to identify then is by putting switch case and manual character code comparison.

Hope that helps
Milind

using System;
using System.CodeDom;
using System.CodeDom.Compiler;
using Microsoft.CSharp;
using System.Text;
using System.Reflection;

///

/// Summary description for Class1.
///

public class Evaluator
{
#region Construction
public Evaluator(EvaluatorItem[] items)
{
ConstructEvaluator(items);
}

public Evaluator(Type returnType, string expression, string name)
{
EvaluatorItem[] items = { new EvaluatorItem(returnType, expression, name) };
ConstructEvaluator(items);
}

public Evaluator(EvaluatorItem item)
{
EvaluatorItem[] items = { item };
ConstructEvaluator(items);
}

private void ConstructEvaluator(EvaluatorItem[] items)
{
ICodeCompiler comp = (new CSharpCodeProvider().CreateCompiler());
CompilerParameters cp = new CompilerParameters();
cp.ReferencedAssemblies.Add("system.dll");
cp.ReferencedAssemblies.Add("system.data.dll");
cp.ReferencedAssemblies.Add("system.xml.dll");
cp.GenerateExecutable = false;
cp.GenerateInMemory = true;

StringBuilder code = new StringBuilder();
code.Append("using System; \n");
code.Append("using System.Data; \n");
code.Append("using System.Data.SqlClient; \n");
code.Append("using System.Data.OleDb; \n");
code.Append("using System.Xml; \n");
code.Append("namespace ADOGuy { \n");
code.Append(" public class _Evaluator { \n");
foreach (EvaluatorItem item in items)
{
code.AppendFormat(" public {0} {1}() ",
item.ReturnType.Name,
item.Name);
code.Append("{ ");
code.AppendFormat(" return ({0}); ", item.Expression);
code.Append("}\n");
}
code.Append("} }");

CompilerResults cr = comp.CompileAssemblyFromSource(cp, code.ToString());
if (cr.Errors.HasErrors)
{
StringBuilder error = new StringBuilder();
error.Append("Error Compiling Expression: ");
foreach (CompilerError err in cr.Errors)
{
error.AppendFormat("{0}\n", err.ErrorText);
}
throw new Exception("Error Compiling Expression: " + error.ToString());
}
Assembly a = cr.CompiledAssembly;
_Compiled = a.CreateInstance("ADOGuy._Evaluator");
}
#endregion

#region Public Members
public int EvaluateInt(string name)
{
return (int)Evaluate(name);
}

public string EvaluateString(string name)
{
return (string)Evaluate(name);
}

public bool EvaluateBool(string name)
{
return (bool)Evaluate(name);
}

public object Evaluate(string name)
{
MethodInfo mi = _Compiled.GetType().GetMethod(name);
return mi.Invoke(_Compiled, null);
}
#endregion

#region Static Members
static public double EvaluateToDouble(string code)
{
Evaluator eval = new Evaluator(typeof(double), code, staticMethodName);
return (double)eval.Evaluate(staticMethodName);
}

static public int EvaluateToInteger(string code)
{
Evaluator eval = new Evaluator(typeof(int), code, staticMethodName);
return (int)eval.Evaluate(staticMethodName);
}

static public string EvaluateToString(string code)
{
Evaluator eval = new Evaluator(typeof(string), code, staticMethodName);
return (string)eval.Evaluate(staticMethodName);
}

static public bool EvaluateToBool(string code)
{
Evaluator eval = new Evaluator(typeof(bool), code, staticMethodName);
return (bool)eval.Evaluate(staticMethodName);
}

static public object EvaluateToObject(string code)
{
Evaluator eval = new Evaluator(typeof(object), code, staticMethodName);
return eval.Evaluate(staticMethodName);
}
#endregion

#region Private
const string staticMethodName = "__foo";
Type _CompiledType = null;
object _Compiled = null;
#endregion
}

public class EvaluatorItem
{
public EvaluatorItem(Type returnType, string expression, string name)
{
ReturnType = returnType;
Expression = expression;
Name = name;
}

public Type ReturnType;
public string Name;
public string Expression;
}



/*
// USE THE FOLLOWING CODE TO EXECUTE...

string sAnswer = Evaluator.EvaluateToDouble("10+15+20-18*2/8").ToString();
*/