extension is not recognized on dynamic field

Question

I used this extension on decimal fields:

public static class Extensions
{
    static System.Globalization.CultureInfo _cultInfo = System.Globalization.CultureInfo.InvariantCulture;
    public static string ConvertToStringWithPointDecimal(this decimal source)
    {
        return source.ToString(_cultInfo);
    }
}

But when I have a dynamic parameter, that contains a class type with decimals in it, I cannot use the extension on those fields.

Test setup:

public class TestDecimalPropClass
{
    public decimal prop1 { get; set; }
    public decimal prop2 { get; set; }
}

private void TryExtensionOnDynamicButton(object sender, EventArgs e)
{
    TestDecimalPropClass _testDecimalPropClass = new TestDecimalPropClass { prop1 = 98765.432M, prop2 = 159.753M };
    TestExtension(_testDecimalPropClass);
}

private void TestExtension(dynamic mySource)
{
    decimal hardDecimal = 123456.789M;
    string resultOutOfHardDecimal = hardDecimal.ConvertToStringWithPointDecimal();

    decimal prop1Decimal = mySource.prop1;
    string resultOutOfProp1Decimal = prop1Decimal.ConvertToStringWithPointDecimal();

    string resultOutOfProp2 = mySource.prop2.ConvertToStringWithPointDecimal();
}}

both resultOutOfHardDecimal and resultOutOfProp1Decimal return a correct string value, but when the code hits mySource.prop2.ConvertToStringWithPointDecimal(), I get this error:"'decimal' does not contain a definition for 'ConvertToStringWithPointDecimal'", while prop2 is of decimal type.

Any thoughts?

Kind regards,

Matthijs

Why not use `Extensions.ConvertToStringWithPointDecimal(mySource.prop2)` directly ? — Alessandro D'Andria, Sep 04 '13 at 10:57
Yeah, quit stupid isn't it. I just didn't think about it. (coffee is almost done). But thanks — user369122, Sep 04 '13 at 11:34
possible duplicate of [Extension method and dynamic object in c#](http://stackoverflow.com/questions/5311465/extension-method-and-dynamic-object-in-c-sharp) — nawfal, Jul 19 '14 at 21:19

score 2 · Accepted Answer · edited May 23 '17 at 12:11

2

Extension methods don't work with dynamics.

Because the C# compiler can't resolve the type of mySource.prop2 at build time, it can't know that it can use the extension method.

However, you can still explicitly call the method:

string resultOutOfProp2 = Extensions.ConvertToStringWithPointDecimal(mySource.prop2);

(like any static method)

See also: Extension method and dynamic object with answers from Jon Skeet and Eric Lippert.

edited May 23 '17 at 12:11

Community

1
1

answered Sep 04 '13 at 11:02

Benoit Blanchon

13,364
4
73
81

Both you and Alessandro D'Andria have got a point here...I need some extra coffee :-) thanks – user369122 Sep 04 '13 at 11:33

extension is not recognized on dynamic field

1 Answers1