ExpressionEval Component

What is ExpressionEval ?

ExpressionEval is an Expression Evaluator back-end component. It allows you to evaluate arbitrary string expressions sush as: logical (Or, And, Not, Xor), comparison (=, <>, <=, <, >, >=) or calculation (+, -, *, /) in an application. Variables and functions can also be used in expressions. The component is configurable: double decimal separator, string tag,… This component is a library provided in .NET Standard 2.0 and in .NET Framework 4.5.

The component is open-source with full functionnalities.

The code source is here: https://github.com/Pierlam/ExpressionEval

Key features

• Input expression as a simple string,
• The expression can be simple or complex,
• Can have nested expression, one or more,
• Comparison operator possible: Or, And, Xor, Not,
• Comparison operator can be defined in english (Or, And, Xor, Not) or in french (Ou, Et, Oux, Non),
• Logical operator possible: =, <>, >, <, >=, <=,
• Calculation operator managed: +, -, * /,
• Value type managed: string, int, double, bool,
• Predefined boolean value can be used: true/False (in english) vrai/faux (in french),
• You can use variable, one or more,
• You can use function call, with parameters or not,
• Wrong expression error management.

Getting started?

Here is a basic general sample which demonstrate how to use the component.

(a=b) and (c>12)

2/ The ExpressionEval component parse the expression.

3/ you have to define and set all used variables present in the expression, for example:

a:=12
b:=12
c:=15

4/ Then the component can evaluate the expression and return the result: true.

So the corresponding source code is :

// Using clauses
using Pierlam.ExpressionEval;
 
// Create the component
ExpressionEval evaluator = new ExpressionEval();
​
// 1-Create the expression to use
string expr= "(a=b) and (c>12)";​
 
// 2-Parse, Decode the expression
evaluator.Parse(expr);
 
// 3-Create variable and provide values
evaluator.DefineVarInt("a", 12);
evaluator.DefineVarInt("b", 12);
evaluator.DefineVarInt("c", 15);
​
// 4-Execute the expression
ExecResult execResult= evaluator.Exec();
 
// Get the result and display it:
Console.WriteLine("Execution Result: " + execResult.ResultBool);

After execution, the console output displays:

Execution Result: true

Because the evaluation of the expression: (12=12) and (15>12) return true.

To use ExpressionEval in your application, get the component from nuget (the nuget link is below).

Get the component

The last available version is: 0.8.

The library is provided in two targets: .NET Standard 2.0 and .NET 4.5

You can get the packet from nuget here: nuget.org/packages/Pierlam.ExpressionEval

Documentation, resources

Code samples

Some code samples are available on github: https://github.com/Pierlam/ExpressionEvalSamples

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This github repository contains a Visual Studio solution within several examples.​

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