You should take the following two steps when applying USPExpress .NET to an expression:

• Parse the expression
  
  • Parsing results in producing an expression tree. Once the tree is built, the expression can be evaluated many times against various variable values.
• Evaluate the expression
  
  • Since the expression tree is already built, evaluation of the expression is performed with maximum possible speed - no additional overhead is involved.

Below is a step-by-step guide to USPExpress usage (in C# syntax):

1. Declare and create USPExpress.USPExpression object:
   
   

   USPExpress.USPExpression cParser;
   cParser = new USPExpress.USPExpression();

2. Specify variables which you intend to use in your expression. Three variables named X1, X2, X3 are specified in the example below:
   
   

   string[] sVariables = new string[]{"X1", "X2", "X3"};

3. Parse the expression:
   
   

   try
   {
      cParser.Parse(sExpression, sVariables);
   }
   catch(USPExpress.ParseException ex)
   {
      //  ...
   }
   

   ParseException is raised, if the expression is not parsed successfully.
   
   
4. Assign actual values to the variables that you specified on step 2:
   
   

   double[] dValues = new double[]{35, 2, 3};

   Or, if you want to evaluate an expression containing DateTime variables:

   object[] oValues = new object[3];
   oValues[0]= 35;
   oValues[1] = 2;
   oValues[2] = Convert.ToDateTime("12.12.2003");

5. Calculate:
   
   

   double dExpValue;
   try
   {
      dExpValue = cParser.Evaluate(dValues);
   }
   catch(UXPExpress.EvaluateException ex)
   {
      //  ...
   }
   

   Or, if you want to evaluate an expression containing DateTime variables:

   string sExpValue;
   try
   {
      sExpValue = cParser.EvaluateEx(oValues);
   }
   catch(UXPExpress.EvaluateException ex)
   {
      //  ...
   }
   

   EvaluateException is raised, if the expression is not evaluated successfully.
   

You may also refer to the Sample projects and the Programmer's Guide document that comes with the library.