Formula in C#.net

Question

Hi,

I'd like to convert a string to a variable formula in C#. I mean that I wanna write as the following.

string formula="a*b";
int a=10;
int b=10;
int ans= formula //here I want to convet formula to.........

Is there any way to solve my problem? Please help me.

Vulpes · Answer

Just remembered that the question was asked under the .NET 3.0/3.5 category so I deduce that you're probably using VS 2008. In that case, I'd suggest making the highlighted alteration to these lines when using integers which you want to be treated as doubles: formula = formula.Replace("a", a.ToString ( "0.0" )); formula = formula.Replace("b", a.ToString ( "0.0" ) ); Hopefully, that will enable the VBScript intrepreter to treat the arguments as doubles and hence produce a double result.

Andry Lebedev · Answer

You can use MathTree lib in MEEL IExpression expression = BaseExpression. Parse ( "x/(95+y)" ) ; IExpression result = expression.Execute();

Vulpes · Answer

Yeah, there has been a change in the way COM libraries work in VS 2010. Previously, COM methods which returned a Variant, returned this to C# code as an 'object'. You then had to cast it back to the exact underlying type or you'd get an exception. VS 2010 (C# 4.0) now uses the 'dynamic' type in this scenario which is more forgiving than 'object'. Basically, if the conversion is valid at runtime, then it's allowed regardless of the underlying type. In fact you don't even need a cast any more. This line works fine in VS 2010: double c = sc.Eval(formula); // no cast needed!

Pravin Ghadge · Answer

Thanks Vulpes for ur reply. Your solutions has solved the problem I am using VS 2005.

Vulpes · Answer

I just tried using double instead of int myself but it worked fine. Are you using VS 2010 and v1.0 of the ScriptControl?

Pravin Ghadge · Answer

Thanks Vulps for ur reply I have used ur code as follows ScriptControl sc=new ScriptControl(); sc.Language = "VBScript"; string formula = "a*b"; double a = 10; double b = 10; formula = formula.Replace("a", a.ToString()); formula = formula.Replace("b", a.ToString()); double c = (double)sc.Eval(formula); Its giving foll. error: "Specified cast is not valid." What mistake i have done?

Vulpes · Answer

What you're trying to do is not possible because methods such as int.Parse, double.Parse etc, do not recognize arithmetic operators such as *, +, - and /. If you're trying to do this for arbitrarily complex formulae, then you need to use an Eval() function such as the one provided by VBScript which can be used from C#. To do this, start a new console application project in VS and add a reference to the Microsoft Script Control 1.0 which can be found under the COM tab. Now enter the following code, build and run: using System.Text; using MSScriptControl; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { var sc = new ScriptControl(); sc.Language = "VBScript"; string formula = "a*b"; int a = 10; int b = 10; formula = formula.Replace("a", a.ToString()); formula = formula.Replace("b", b.ToString()); int c = (int)sc.Eval(formula); Console.WriteLine("Result: " + c); Console.ReadKey(); } } }

Pravin Ghadge · Answer

Actually i cant set Formula as integer. Because i am keeping formula in formula master table. In formula master, i have used 2 fields:1)Formula_Name & 2) Formula_String EG: Formula MAster Table: FormulaName Formula_String SquareArea Width*Width RectangleArea Width*Length

Pravin Ghadge · Answer

Jitendra, I have tried ur code. bt it is not solving my issues.

Pravin Ghadge · Answer

Hi Jitendra Actually iam trying to fix formula in string & then calculating values using that formula. Is it possible? Eg: string formula = "a*b"; int a = 10; int b = 10; int c; formula = formula.Replace("a", a.ToString()); formula = formula.Replace("b", a.ToString()); c = int.Parse(formula); It giving me foll error: "Input string was not in a correct format." Plz Plz help me out.

Jiteendra Sampathirao · Answer

try this: int a = 10; int b = 20; int x = a * b; string y = Convert.ToString(x); int z = Convert.ToInt32(y);

Jiteendra Sampathirao · Answer

try this: string y = "result is" + a * b+ "Hope this help you";

Jiteendra Sampathirao · Answer

Hi pravin, int a = 10; int b = 20; int x = a * b; Console.WriteLine("Result:" + x);

Formula in C#.net

Answers (13)