Using Math Parser COM Component in C#

bcParserX COM Component can be used from managed code as well as native code. Here we will show a simple C# (csharp) console application to demonstrate simple the steps required to get math expression parser working.

The sample starts with creating a instance of the COM object to use. Then we set the expression to parse. Then we assign predefined variables X and Y. And we create a new variable called Z. Notice that this sample intentionally fogets to create variable K. Then we evaluate the expression and display the result. When we execute this code, we get an exception that says expression is not valid. In the catch block, we display this error. Then we also display the invalid portion of the expression which says �K�. This functionality is useful for some applications that wish to recover from certain errors by defining K and continue.

Step 1: To be able to use the COM component, you need to add a reference to it in your project:

Step 2: Type the Code: using BCPARSERLib;

using System; using BCPARSERLib; //using System.Runtime.InteropServices; namespace CSharpExample {         /// <summary>         /// Summary description for Class1.         /// </summary>         class Class1         {                 /// <summary>                 /// The main entry point for the application.                 /// </summary>                 [STAThread]                 static void Main(string[] args)                 {                         Parser p = new ParserClass(); //new parser instance.                         try                         {                                 p.Expression = "x+y+z+k"; //notice that k is not valid.                                         p.X = 5; //assign predefined var X.                                 p.Y = 6; //assign predefined var Y.                                 p.set_Variable("Z", 1); //create new var Z.                                 double value = p.Evaluate(); //get result.                                 Console.WriteLine("Answer="+value);                         }                         catch(Exception ex)                         {                                 Console.WriteLine(ex.Message);                                 Console.WriteLine("Invalid syntax is: "+                                         p.GetInvalidPortionOfExpression());                         }                         Console.WriteLine("Press Enter to Exit.");                         Console.ReadLine();                 }         } }

As simple as that! And now you can have powerful math expression parsing capabilities in your application with few lines of code too!

Step 3: Execute! When you run this application, output is:

Adding User Defined Functions to Math Parser COM Component in C#

To add user defined custom functions to the bcParserX COM Component, you need to use the �Parser� class which has support for events. Event handlers are registered using the C# delegate syntax the usual way as seen in below code. This is possible because when you use the COM component from C# code, Visual Studio generate a COM interoperability wrapper DLL and class which wraps the COM component and makes the functionality available as managed code.

using System; using BCPARSERLib; //using System.Runtime.InteropServices; namespace CSharpExample {         /// <summary>         /// Summary description for Class1.         /// </summary>         class Class1         {                 /// <summary>                 /// The main entry point for the application.                 /// </summary>                 [STAThread]                 static void Main(string[] args)                 {                         Parser p = new ParserClass(); //new parser instance.                         try                         {                                 //You can register your own event handlers to create custom functions:                                 p.OnExecOneParamFunc += new _IParserEvents_OnExecOneParamFuncEventHandler(onExecOneParamFunc);                                 p.OnExecTwoParamFunc += new _IParserEvents_OnExecTwoParamFuncEventHandler(onExecTwoParamFunc);                                 p.OnExec3ParamFunc += new _IParserEvents_OnExec3ParamFuncEventHandler(onExec3ParamFunc);                                 p.OnExecNParamFunc += new _IParserEvents_OnExecNParamFuncEventHandler(onExecNParamFunc);                                                                 //p.Expression = "x+y+z+k"; //notice that k is not valid.                                 //Register your own function names:                                 p.CreateOneParamFunc("ONE");                                 p.CreateTwoParamFunc("TWO");                                 p.Create3ParamFunc("THREE");                                 p.CreateNParamFunc("NP");                                 p.Expression = "NP(1,2,3,4)+ONE(1)+TWO(2,3)+THREE(1,2,3)+X";                                 //p.Expression = "AVG(7, 5)";                                                                 p.X = 5; //assign predefined var X.                                 p.Y = 6; //assign predefined var Y.                                 p.set_Variable("Z", 1); //create new var Z.                                 double value = p.Evaluate(); //get result.                                 Console.WriteLine("Answer="+value);                         }                         catch(Exception ex)                         {                                 Console.WriteLine(ex.Message);                                 Console.WriteLine("Invalid syntax is: "+                                         p.GetInvalidPortionOfExpression());                         }                         Console.WriteLine("Press Enter to Exit.");                         Console.ReadLine();                 }                 /// <summary>                 /// Event handler to return the value of user defined functions that take one parameter.                 /// Math Parser will report syntax error if exactly 1 parameter is not passed to invoke a                 /// user defined function that is registered as a 1 parameter function.                 /// </summary>                 /// <param name="funcName">The function name whose value should be returned.</param>                 /// <param name="p">The parameter value that the user defined function takes.</param>                 /// <returns>Value of the user defined function funcName.</returns>                 static public double onExecOneParamFunc(string funcName, double p)                 {                         if(funcName.Equals("ONE"))                         {                                 return p+1; //do something with parameters.                         }                         throw new Exception("Unexpected function name: "+funcName);                 }                 /// <summary>                 /// Event handler to return the value of user defined functions that take two parameter.                 /// Math Parser will report syntax error if exactly 2 parameters are not passed to invoke a                 /// user defined function that is registered as a 2 parameter function.                 /// </summary>                 /// <param name="funcName">The function name whose value should be returned.</param>                 /// <param name="p1">The first parameter value that the user defined function takes.</param>                 /// <param name="p2">The second parameter value that the user defined function takes.</param>                 /// <returns>Value of the user defined function funcName.</returns>                 static public double onExecTwoParamFunc(string funcName, double p1, double p2)                 {                         Console.WriteLine("FuncName: "+funcName);                         if(funcName.Equals("TWO"))                         {                                 Console.WriteLine("Returning: "+(p1+p2+2));                                 return p1+p2+2; //do something with parameters.                         }                         throw new Exception("Unexpected function name: "+funcName);                 }                 /// <summary>                 /// Event handler to return the value of user defined functions that take three parameters.                 /// Math Parser will report syntax error if exactly 3 parameters are not passed to invoke a                 /// user defined function that is registered as a 3 parameter function.                 /// </summary>                 /// <param name="funcName">The function name whose value should be returned.</param>                 /// <param name="p1">The first parameter value that the user defined function takes.</param>                 /// <param name="p2">The second parameter value that the user defined function takes.</param>                 /// <param name="p3">The second parameter value that the user defined function takes.</param>                 /// <returns>Value of the user defined function funcName.</returns>                 static public double onExec3ParamFunc(string funcName, double p1, double p2, double p3)                 {                         if(funcName.Equals("THREE"))                         {                                 return p1+p2+p3+3; //do something with parameters.                         }                         throw new Exception("Unexpected function name: "+funcName);                 }                 /// <summary>                 /// Event handler to return the value of user defined functions that take any numbers of parameters.                 /// Enforcement of the correct number of parameters that a function supports is done within this                 /// event handler. Math Parser will not accept any number of parameters and your event handler needs                 /// to decide whether a particular set of parameters are ok or not.                 /// </summary>                 /// <param name="funcName">The function name whose value should be returned.</param>                 /// <param name="values">The parameters that the user defined function takes are passed in                 /// as System.Array.</param>                 /// <returns>Value of the user defined function funcName.</returns>                 static public double onExecNParamFunc(string funcName, ref System.Array values)                 {                         Console.WriteLine("FuncName is: "+funcName);                         if(funcName.Equals("NP"))                         {                                 if(values.GetLength(0)!=4)                                 {                                         throw new Exception("NP function requires 4 parameters. "+                                                 "Number of parameters passed: "+values.GetLength(0));                                 }                                 double val = (Double)values.GetValue(0)+(Double)values.GetValue(3);                                 Console.WriteLine("Returning: "+val);                                 return val;                         }                         throw new Exception("Unexpected function name: "+funcName);                 }         } }

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