Expression Evaluator Compile Multiple Statements

Scripts are nothing but just a series of expressions separated by ; character. The ExpressionEvaluator gives you the ability to compile several statements into one function using the ExpressionType property of the CompiledExpression object.

The following example evaluates the script, which contains multiple if and elseif statements.

public static void Example1()
{
    string script = @"
        
        if ( a.Marks >= 80)
        {
            a.Grade = 'A';
        }
        else if (a.Marks >= 70)
        {
            a.Grade = 'B';
        }
        else if(a.Marks >= 60)
        {
            a.Grade = 'C';
        }
        else if(a.Marks >= 50)
        {
            a.Grade = 'D';
        }
        else
        {
            a.Grade = 'F';
        }
        ";

    var myClass = new MyClass() { Marks = 79 };

    var register = new TypeRegistry();
    register.RegisterSymbol("a", myClass);

    var expression = new CompiledExpression(script) 
    { 
        TypeRegistry = register, 
        ExpressionType = CompiledExpressionType.StatementList 
    };    

    expression.Eval();
    Console.WriteLine("Grade: {0}", myClass.Grade);
}

Now let's execute the above code, and you will see the following output.

Grade: B

To compile multiple statements, simply set the ExpressionType property to CompiledExpressionType.StatementList before any of the Eval or Compile methods are called.