How do I check if a property exists on a dynamic anonymous type in c#?

Question

I have an anonymous type object that I receive as a dynamic from a method I would like to check in a property exists on that object.

....
var settings = new {
                   Filename="temp.txt",
                   Size=10
}
...

function void Settings(dynamic settings) {
var exists = IsSettingExist(settings,"Filename")
}

How would I implement IsSettingExist ?

Izanagi

Possible duplicate of How to detect if a property exists on an ExpandoObject? – Discourteous

If you find your self heavily relying on dynamic objects its probably worth looking at F# - Nice Avatar by the way – Joppa

Answer 1

  public static bool DoesPropertyExist(dynamic settings, string name)
  {
    if (settings is ExpandoObject)
      return ((IDictionary<string, object>)settings).ContainsKey(name);

    return settings.GetType().GetProperty(name) != null;
  }

  var settings = new {Filename = @"c:\temp\q.txt"};
  Console.WriteLine(DoesPropertyExist(settings, "Filename"));
  Console.WriteLine(DoesPropertyExist(settings, "Size"));

Output:

 True
 False

Kismet

This does not work on dynamic objects. It always returns null. – Diegodiehard

@Diegodiehard @Shikasta_Kashti Are you trying to use this method with an MVC ViewBag? If so, see https://mcmap.net/q/110897/-how-to-detect-if-a-property-exists-on-an-expandoobject – Katlaps

@Gaspa79. It's a not-uncommon coding convention. Some folks like an "Is" prefix on all boolean properties. Consistency like that can prevent you from having to guess the first few characters of an identifier (after which, Intellisense works), but at the expense of making a little awkward English in cases like this. – Adelaidaadelaide

I find the invalid verb tense of the Is prefix to be more confusing than it would be otherwise to use HasProperty. I would also say that using a grammatically-incorrect prefix like this is actually non-idiomatic in C♯. – Delilahdelimit

ExpandoObject is not the same thing as anonymous type. Am I wrong about that? – Viperish

A bit of description and links could have been helpful – Sev

Answer 2

public static bool HasProperty(dynamic obj, string name)
{
    Type objType = obj.GetType();

    if (objType == typeof(ExpandoObject))
    {
        return ((IDictionary<string, object>)obj).ContainsKey(name);
    }

    return objType.GetProperty(name) != null;
}

Sepulveda

Answer 3

This works for anonymous types, ExpandoObject, Nancy.DynamicDictionary or anything else that can be cast to IDictionary<string, object>.

    public static bool PropertyExists(dynamic obj, string name) {
        if (obj == null) return false;
        if (obj is IDictionary<string, object> dict) {
            return dict.ContainsKey(name);
        }
        return obj.GetType().GetProperty(name) != null;
    }

Rheumatic

Great solution. I needed to add one more IF statement when converting JSON string into JObject...."if (obj is Newtonsoft.Json.Linq.JObject) return ((Newtonsoft.Json.Linq.JObject)obj).ContainsKey(name);" – Campney

Also worked for me. Wonderful answer Seth Reno. I have also added "if (obj is Newtonsoft.Json.Linq.JObject) return ((Newtonsoft.Json.Linq.JObject)obj).ContainsKey(name);" in above function as suggested by rr789. So please also edit your answer to include it. – Jenellejenesia

Thank you @BrijeshKumarTripathi! This was exactly my scenario. – Viperish

Answer 4

if you can control creating/passing the settings object, i'd recommend using an ExpandoObject instead.

dynamic settings = new ExpandoObject();
settings.Filename = "asdf.txt";
settings.Size = 10;
...

function void Settings(dynamic settings)
{
    if ( ((IDictionary<string, object>)settings).ContainsKey("Filename") )
        .... do something ....
}

Blooper

I can't change it, can I cast to ExpendoObject? – Izanagi

Answer 5

I ran into the dynamic was Newtonsoft.Json.Linq.JObject instead of IDictionary

I added and extra if and it works.

public static bool PropertyExists(dynamic obj, string name)
{
    if (obj == null) return false;

    else if (obj is IDictionary<string, object> dict)
    {
        return dict.ContainsKey(name);
    }

    else if (obj is Newtonsoft.Json.Linq.JObject jObject)
    {
        return jObject.ContainsKey(name);
    }

    else
    {
        return obj.GetType().GetProperty(name) != null;
    }
}

Edit smarter solution than the previous using switch expression

public static bool PropertyExists(dynamic obj, string name)
{
    if (obj == null) return false;
    return obj switch
    {
        IDictionary<string, object> dict => dict.ContainsKey(name),
        Newtonsoft.Json.Linq.JObject jObject => jObject.ContainsKey(name),
        _ => obj.GetType().GetProperty(name) != null
    };
}

Docila

The 1st is a great solution. The "smarter" is not actually smarter. Just shorter and more difficult to understand. – Chord

Answer 6

In case someone need to handle a dynamic object come from Json, I has modified Seth Reno answer to handle dynamic object deserialized from NewtonSoft.Json.JObjcet.

public static bool PropertyExists(dynamic obj, string name)
    {
        if (obj == null) return false;
        if (obj is ExpandoObject)
            return ((IDictionary<string, object>)obj).ContainsKey(name);
        if (obj is IDictionary<string, object> dict1)
            return dict1.ContainsKey(name);
        if (obj is IDictionary<string, JToken> dict2)
            return dict2.ContainsKey(name);
        return obj.GetType().GetProperty(name) != null;
    }

Earldom

Answer 7

Merging and fixing answers from Serj-TM and user3359453 so that it works with both ExpandoObject and DynamicJsonObject. This works for me.

public static bool HasPropertyExist(dynamic settings, string name)
{
    if (settings is System.Dynamic.ExpandoObject)
        return ((IDictionary<string, object>)settings).ContainsKey(name);

    if (settings is System.Web.Helpers.DynamicJsonObject)
    try
    {
        return settings[name] != null;
    }
    catch (KeyNotFoundException)
    {
        return false;
    }


    return settings.GetType().GetProperty(name) != null;
}

Cooky

Answer 8

This is working for me-:

  public static bool IsPropertyExist(dynamic dynamicObj, string property)
       {
           try
           {
               var value=dynamicObj[property].Value;
               return true;
           }
           catch (RuntimeBinderException)
           {

               return false;
           }

       }

Sullivan

Allowing exceptions to occur and then catching them is not a preferred solution because there is a lot of overhead associated with throwing and catching. It's a last resort only. Exceptions are for designed for situations that should not happen in the course of execution like a network being unavailable. There are much better solutions here. – Agleam

Fails with RuntimeBinderException and dynamicObj[property].Value when value is actually there ... var value = dynamicObj[property] is enough ... and when it does not exist KeyNotFoundException on Dictionary is thrown... see below... – Legate

It's not acceptable solution to use exceptions in business logic. 1 grade, 2nd term. – Ducks

Answer 9

Using reflection, this is the function i use :

public static bool doesPropertyExist(dynamic obj, string property)
{
    return ((Type)obj.GetType()).GetProperties().Where(p => p.Name.Equals(property)).Any();
}

then..

if (doesPropertyExist(myDynamicObject, "myProperty")){
    // ...
}

Daube

GetProperties() doesn't list dynamic Member on a DynamicObject. There is a dedicated function GetDynamicMemberNames() for that. – Tersanctus

Using the lambda expression Where first, and then Any is redundant, as you can formulate your filtering expression in Anyas well. – Blades

Answer 10

To extend the answer from @Kuroro, if you need to test if the property is empty, below should work.

public static bool PropertyExistsAndIsNotNull(dynamic obj, string name)
{
    if (obj == null) return false;
    if (obj is ExpandoObject)
    {
        if (((IDictionary<string, object>)obj).ContainsKey(name))
            return ((IDictionary<string, object>)obj)[name] != null;
        return false;
    }
    if (obj is IDictionary<string, object> dict1)
    {
        if (dict1.ContainsKey(name))
            return dict1[name] != null;
        return false;
    }
    if (obj is IDictionary<string, JToken> dict2)
    {
        if (dict2.ContainsKey(name))
            return (dict2[name].Type != JTokenType.Null && dict2[name].Type != JTokenType.Undefined);
        return false;
    }
    if (obj.GetType().GetProperty(name) != null)
        return obj.GetType().GetProperty(name).GetValue(obj) != null;
    return false;
}

Infantryman

Answer 11

None of the solutions above worked for dynamic that comes from Json, I however managed to transform one with Try catch (by @user3359453) by changing exception type thrown (KeyNotFoundException instead of RuntimeBinderException) into something that actually works...

public static bool HasProperty(dynamic obj, string name)
    {
        try
        {
            var value = obj[name];
            return true;
        }
        catch (KeyNotFoundException)
        {
            return false;
        }
    }

Hope this saves you some time.

Legate

Using exceptions for things like these is not recommended. Should've gone for something like casting to JObject and using .Property() != null – Subtenant

Answer 12

    public static void Test()
    {
        int LOOP_LENGTH = 100000000;
        {
            long first_memory = GC.GetTotalMemory(true);
            var stopWatch = Stopwatch.StartNew();

            Console.WriteLine("doesPropertyExist");

            dynamic testdo = new { A = 1, B = (string)null, C = "A" };
            for (int i = 0; i < LOOP_LENGTH; i++)
            {
                if (!TestDynamic.doesPropertyExist(testdo, "A"))
                {
                    Console.WriteLine("throw find");
                    break;
                }

                if (TestDynamic.doesPropertyExist(testdo, "ABC"))
                {
                    Console.WriteLine("throw not find");
                    break;
                }
            }
            stopWatch.Stop();
            var last_memory = GC.GetTotalMemory(true);
            Console.WriteLine($" Time:{stopWatch.Elapsed.TotalSeconds}s\t Memory:{last_memory - first_memory}");
        }

        {
            long first_memory = GC.GetTotalMemory(true);
            var stopWatch = Stopwatch.StartNew();

            Console.WriteLine("HasProperty");

            dynamic testdo = new { A = 1, B = (string)null, C = "A" };
            for (int i = 0; i < LOOP_LENGTH; i++)
            {
                if (!TestDynamic.HasProperty(testdo, "A"))
                {
                    Console.WriteLine("throw find");
                    break;
                }

                if (TestDynamic.HasProperty(testdo, "ABC"))
                {
                    Console.WriteLine("throw not find");
                    break;
                }
            }
            stopWatch.Stop();
            var last_memory = GC.GetTotalMemory(true);
            Console.WriteLine($" Time:{stopWatch.Elapsed.TotalSeconds}s\t Memory:{last_memory - first_memory}");
        }


        {
            long first_memory = GC.GetTotalMemory(true);
            var stopWatch = Stopwatch.StartNew();

            Console.WriteLine("IsPropertyExist");

            dynamic testdo = new { A = 1, B = (string)null, C = "A" };
            for (int i = 0; i < LOOP_LENGTH; i++)
            {
                if (!TestDynamic.IsPropertyExist(testdo, "A"))
                {
                    Console.WriteLine("throw find");
                    break;
                }

                if (TestDynamic.IsPropertyExist(testdo, "ABC"))
                {
                    Console.WriteLine("throw not find");
                    break;
                }
            }
            stopWatch.Stop();
            var last_memory = GC.GetTotalMemory(true);
            Console.WriteLine($" Time:{stopWatch.Elapsed.TotalSeconds}s\t Memory:{last_memory - first_memory}");
        }

        {
            long first_memory = GC.GetTotalMemory(true);
            var stopWatch = Stopwatch.StartNew();

            Console.WriteLine("IsPropertyExistBinderException");

            dynamic testdo = new { A = 1, B = (string)null, C = "A" };
            for (int i = 0; i < LOOP_LENGTH; i++)
            {
                if (!TestDynamic.IsPropertyExistBinderException(testdo, "A"))
                {
                    Console.WriteLine("throw find");
                    break;
                }

                if (TestDynamic.IsPropertyExistBinderException(testdo, "ABC"))
                {
                    Console.WriteLine("throw not find");
                    break;
                }
            }
            stopWatch.Stop();
            var last_memory = GC.GetTotalMemory(true);
            Console.WriteLine($" Time:{stopWatch.Elapsed.TotalSeconds}s\t Memory:{last_memory - first_memory}");
        }


        {
            long first_memory = GC.GetTotalMemory(true);
            var stopWatch = Stopwatch.StartNew();

            Console.WriteLine("PropertyExists");

            dynamic testdo = new { A = 1, B = (string)null, C = "A" };
            for (int i = 0; i < LOOP_LENGTH; i++)
            {
                if (!TestDynamic.PropertyExists(testdo, "A"))
                {
                    Console.WriteLine("throw find");
                    break;
                }

                if (TestDynamic.PropertyExists(testdo, "ABC"))
                {
                    Console.WriteLine("throw not find");
                    break;
                }
            }
            stopWatch.Stop();
            var last_memory = GC.GetTotalMemory(true);
            Console.WriteLine($" Time:{stopWatch.Elapsed.TotalSeconds}s\t Memory:{last_memory - first_memory}");
        }


        {
            long first_memory = GC.GetTotalMemory(true);
            var stopWatch = Stopwatch.StartNew();

            Console.WriteLine("PropertyExistsJToken");

            dynamic testdo = new { A = 1, B = (string)null, C = "A" };
            for (int i = 0; i < LOOP_LENGTH; i++)
            {
                if (!TestDynamic.PropertyExistsJToken(testdo, "A"))
                {
                    Console.WriteLine("throw find");
                    break;
                }

                if (TestDynamic.PropertyExistsJToken(testdo, "ABC"))
                {
                    Console.WriteLine("throw not find");
                    break;
                }
            }
            stopWatch.Stop();
            var last_memory = GC.GetTotalMemory(true);
            Console.WriteLine($" Time:{stopWatch.Elapsed.TotalSeconds}s\t Memory:{last_memory - first_memory}");
        }




    }

    public static bool IsPropertyExist(dynamic settings, string name)
    {
        if (settings is ExpandoObject)
            return ((IDictionary<string, object>)settings).ContainsKey(name);

        return settings.GetType().GetProperty(name) != null;
    }

    public static bool HasProperty(dynamic obj, string name)
    {
        Type objType = obj.GetType();

        if (objType == typeof(ExpandoObject))
        {
            return ((IDictionary<string, object>)obj).ContainsKey(name);
        }

        return objType.GetProperty(name) != null;
    }


    public static bool PropertyExists(dynamic obj, string name)
    {
        if (obj == null) return false;
        if (obj is IDictionary<string, object> dict)
        {
            return dict.ContainsKey(name);
        }
        return obj.GetType().GetProperty(name) != null;
    }

    // public static bool HasPropertyExist(dynamic settings, string name)
    // {
    //     if (settings is System.Dynamic.ExpandoObject)
    //         return ((IDictionary<string, object>)settings).ContainsKey(name);
    //     if (settings is DynamicJsonObject)
    //         try
    //         {
    //             return settings[name] != null;
    //         }
    //         catch (KeyNotFoundException)
    //         {
    //             return false;
    //         }
    //     return settings.GetType().GetProperty(name) != null;
    // }

    public static bool IsPropertyExistBinderException(dynamic dynamicObj, string property)
    {
        try
        {
            var value = dynamicObj[property].Value;
            return true;
        }
        catch (RuntimeBinderException)
        {

            return false;
        }

    }

    public static bool HasPropertyFoundException(dynamic obj, string name)
    {
        try
        {
            var value = obj[name];
            return true;
        }
        catch (KeyNotFoundException)
        {
            return false;
        }
    }


    public static bool doesPropertyExist(dynamic obj, string property)
    {
        return ((Type)obj.GetType()).GetProperties().Where(p => p.Name.Equals(property)).Any();
    }

    public static bool PropertyExistsJToken(dynamic obj, string name)
    {
        if (obj == null) return false;
        if (obj is ExpandoObject)
            return ((IDictionary<string, object>)obj).ContainsKey(name);
        if (obj is IDictionary<string, object> dict1)
            return dict1.ContainsKey(name);
        if (obj is IDictionary<string, JToken> dict2)
            return dict2.ContainsKey(name);
        return obj.GetType().GetProperty(name) != null;
    }

    // public static bool PropertyExistsJsonObject(dynamic settings, string name)
    // {
    //     if (settings is ExpandoObject)
    //         return ((IDictionary<string, object>)settings).ContainsKey(name);
    //     else if (settings is DynamicJsonObject)
    //         return ((DynamicJsonObject)settings).GetDynamicMemberNames().Contains(name);

    //     return settings.GetType().GetProperty(name) != null;
    // }
}

doesPropertyExist

Time:59.5907507s Memory:403680

HasProperty

Time:30.8231781s Memory:14968

IsPropertyExist

Time:39.6179575s Memory:97000

IsPropertyExistBinderException throw find

PropertyExists

Time:56.009761s Memory:13464

PropertyExistsJToken

Time:61.6146953s Memory:15952

Jermaine

Answer 13

This works also for DynamicJsonObject:

  public static bool PropertyExists(dynamic settings, string name)
  {
    if (settings is ExpandoObject)
      return ((IDictionary<string, object>)settings).ContainsKey(name);
    else if (settings is DynamicJsonObject)
      return ((DynamicJsonObject)settings).GetDynamicMemberNames().Contains(name);

    return settings.GetType().GetProperty(name) != null;
  }

Permeate

Answer 14

To save others some time and this answer covers a lot of the people Googling this question using Newtonstoft Json deserialization with dynamics:

dynamic dynamicObject = JsonConvert.DeserializeObject<dynamic>(json);
if (IsContainsKey(dynamicObject, "searchText"))
    searchText = dynamicObject.searchText;

bool IsContainsKey(dynamic newtonsoftDynamic, string propertyName) {
    return (newtonsoftDynamic as JObject).ContainsKey(propertyName);
}

or just in code:

JObject obj = dynamicObject as JObject;
string searchText = string.Empty;
if (obj.ContainsKey("searchText"))
    searchText = obj.Value<string>("searchText");

no exceptions, proper handling via Newtonsoft but you can still use the dynamicObject.xxx for properties you know will always be there.

Nellie