Is there an eval function In C#?

Question

I\'m typing an equation into a TextBox that will generate the graph of the given parabola. Is it possible to use an eval function? I\'m using C# 2010 and it doesn\'t have Mi

Answer 1

C# doesn't have a comparable Eval function but creating one is really easy:

public static double Evaluate(string expression)  
       {  
           System.Data.DataTable table = new System.Data.DataTable();  
           table.Columns.Add("expression", string.Empty.GetType(), expression);  
           System.Data.DataRow row = table.NewRow();  
           table.Rows.Add(row);  
           return double.Parse((string)row["expression"]);  
       }

Now simply call it like this:

Console.WriteLine(Evaluate("9 + 5"));

Answer 2

Thank you so much Mr.Teoman Soygul

if you want to catch the error then you can use try catch,then we can use that values to future purpose.

try
{
    DataTable table = new System.Data.DataTable();
    table.Columns.Add("expression", string.Empty.GetType(), expression);
    DataRow row = table.NewRow();
    table.Rows.Add(row);
    return double.Parse((string)row["expression"]);
}
catch (Exception)
{
    return -1;
}

Answer 3

I created the ExpressionEvaluatorCs Nuget package inspired by mar.k's answer and also added the option to specify return type.

Sample code

// Returns object 6
object result1 = ExpressionEvaluator.Evaluate("(1 + 2) * 2");

// Returns int 6
int result1 = ExpressionEvaluator.Evaluate<int>("(1 + 2) * 2");

Answer 4

You can create one yourself by using CodeDom. It will be slow because it creates a new assembly every time you call Eval.

public class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine(ExpressionEvaluator.Eval("(2 + 2) * 2"));
    }
}

public class ExpressionEvaluator
{
    public static double Eval(string expression)
    {
        CSharpCodeProvider codeProvider = new CSharpCodeProvider();
        CompilerResults results =
            codeProvider
            .CompileAssemblyFromSource(new CompilerParameters(), new string[]
            {
                string.Format(@"
                    namespace MyAssembly
                    {{
                        public class Evaluator
                        {{
                            public double Eval()
                            {{
                                return {0};
                            }}
                        }}
                    }}

                ",expression)
            });

        Assembly assembly = results.CompiledAssembly;
        dynamic evaluator = 
            Activator.CreateInstance(assembly.GetType("MyAssembly.Evaluator"));
        return evaluator.Eval();
    }
}

Answer 5

There is no native C# eval function; but as others have previously stated, there are several workarounds for what you are trying to do.

If you're interested in evaluating more complicated C# code, my C# eval program provides for evaluating C# code at runtime and supports many C# statements. In fact, this code is usable within any .NET project, however, it is limited to using C# syntax. Have a look at my website, http://csharp-eval.com, for additional details.

Answer 6

You can easily do this with the "Compute" method of the DataTable class.

static Double Eval(String expression)
{
    System.Data.DataTable table = new System.Data.DataTable();
    return Convert.ToDouble(table.Compute(expression, String.Empty));
}

Pass a term in form of a string to the function in order to get the result.

Double result = Eval("7 * 6");
result = Eval("17 + 4");
...