Get value of c# dynamic property via string

Once you have your PropertyInfo (from GetProperty), you need to call GetValue and pass in the instance that you want to get the value from. In your case:

d.GetType().GetProperty("value2").GetValue(d, null);

public static object GetProperty(object target, string name)
{
    var site = System.Runtime.CompilerServices.CallSite<Func<System.Runtime.CompilerServices.CallSite, object, object>>.Create(Microsoft.CSharp.RuntimeBinder.Binder.GetMember(0, name, target.GetType(), new[]{Microsoft.CSharp.RuntimeBinder.CSharpArgumentInfo.Create(0,null)}));
    return site.Target(site, target);
}

Add reference to Microsoft.CSharp. Works also for dynamic types and private properties and fields.

Edit: While this approach works, there is almost 20× faster method from the Microsoft.VisualBasic.dll assembly:

public static object GetProperty(object target, string name)
{
    return Microsoft.VisualBasic.CompilerServices.Versioned.CallByName(target, name, CallType.Get);
}

Dynamitey is an open source .net std library, that let's you call it like the dynamic keyword, but using the a string for the property name rather than the compiler doing it for you, and it ends up being equal to reflection speedwise (which is not nearly as fast as using the dynamic keyword, but this is due to the extra overhead of caching dynamically, where the compiler caches statically).

Dynamic.InvokeGet(d,"value2");

The easiest method for obtaining both a setter and a getter for a property which works for any type including dynamic and ExpandoObject is to use FastMember which also happens to be the fastest method around (it uses Emit).

You can either get a TypeAccessor based on a given type or an ObjectAccessor based of an instance of a given type.

Example:

var staticData = new Test { Id = 1, Name = "France" };
var objAccessor = ObjectAccessor.Create(staticData);
objAccessor["Id"].Should().Be(1);
objAccessor["Name"].Should().Be("France");

var anonymous = new { Id = 2, Name = "Hilton" };
objAccessor = ObjectAccessor.Create(anonymous);
objAccessor["Id"].Should().Be(2);
objAccessor["Name"].Should().Be("Hilton");

dynamic expando = new ExpandoObject();
expando.Id = 3;
expando.Name = "Monica";
objAccessor = ObjectAccessor.Create(expando);
objAccessor["Id"].Should().Be(3);
objAccessor["Name"].Should().Be("Monica");

var typeAccessor = TypeAccessor.Create(staticData.GetType());
typeAccessor[staticData, "Id"].Should().Be(1);
typeAccessor[staticData, "Name"].Should().Be("France");

typeAccessor = TypeAccessor.Create(anonymous.GetType());
typeAccessor[anonymous, "Id"].Should().Be(2);
typeAccessor[anonymous, "Name"].Should().Be("Hilton");

typeAccessor = TypeAccessor.Create(expando.GetType());
((int)typeAccessor[expando, "Id"]).Should().Be(3);
((string)typeAccessor[expando, "Name"]).Should().Be("Monica");

Much of the time when you ask for a dynamic object, you get an ExpandoObject (not in the question's anonymous-but-statically-typed example above, but you mention JavaScript and my chosen JSON parser JsonFx, for one, generates ExpandoObjects).

If your dynamic is in fact an ExpandoObject, you can avoid reflection by casting it to IDictionary, as described at http://msdn.microsoft.com/en-gb/library/system.dynamic.expandoobject.aspx.

Once you've cast to IDictionary, you have access to useful methods like .Item and .ContainsKey

The GetProperty/GetValue does not work for Json data, it always generate a null exception, however, you may try this approach:

Serialize your object using JsonConvert:

var z = Newtonsoft.Json.JsonConvert.DeserializeObject(Convert.ToString(request));

Then access it directly casting it back to string:

var pn = (string)z["DynamicFieldName"];

It may work straight applying the Convert.ToString(request)["DynamicFieldName"], however I haven't tested.

d.GetType().GetProperty("value2")

returns a PropertyInfo object.

So then do

propertyInfo.GetValue(d)

This is the way i ve got the value of a property value of a dinamic:

    public dynamic Post(dynamic value)
    {            
        try
        {
            if (value != null)
            {
                var valorCampos = "";

                foreach (Newtonsoft.Json.Linq.JProperty item in value)
                {
                    if (item.Name == "valorCampo")//property name
                        valorCampos = item.Value.ToString();
                }                                           

            }
        }
        catch (Exception ex)
        {

        }


    }

To get properties from dynamic doc when .GetType() returns null, try this:

var keyValuePairs = ((System.Collections.Generic.IDictionary<string, object>)doc);
var val = keyValuePairs["propertyName"].ToObject<YourModel>;

In .Net core 3.1 you can try like this

d?.value2 , d?.value3

Some of the solutions were not working with a valuekind object that I obtained from a json string, maybe because I did not have a concrete type in my code that was similar to the object that I would obtain from the json string, so how I went about it was

JsonElement myObject = System.Text.Json.JsonSerializer.Deserialize<JsonElement>(jsonStringRepresentationOfMyObject);

/*In this case I know that there is a property with 
the name Code, otherwise use TryGetProperty. This will 
still return a JsonElement*/

JsonElement propertyCode = myObject.GetProperty("Code");
        
/*Now with the JsonElement that represents the property, 
you can use several methods to retrieve the actual value, 
in this case I know that the value in the property is a string, 
so I use the GetString method on the object. If I knew the value 
was a double, then I would use the GetDouble() method on the object*/

string code = propertyCode.GetString();

That worked for me

Similar to the accepted answer, you can also try GetField instead of GetProperty.

d.GetType().GetField("value2").GetValue(d);

Depending on how the actual Type was implemented, this may work when GetProperty() doesn't and can even be faster.

In case you have a dynamic variable such as a DapperRow for example you can first build up an ExpandoObject, then cast the Expando into an IDictionary. From then on, getting a value via the name of a property is possible.

Helper method ToExpandoObject:

public static ExpandoObject ToExpandoObject(object value)
    {
        IDictionary<string, object> dapperRowProperties = value as IDictionary<string, object>;
        IDictionary<string, object> expando = new ExpandoObject();
        if (dapperRowProperties == null)
        {
            return expando as ExpandoObject;
        }
        foreach (KeyValuePair<string, object> property in dapperRowProperties)
        {
            if (!expando.ContainsKey(property.Key))
            {
                expando.Add(property.Key, property.Value);
            }
            else
            {
                //prefix the colliding key with a random guid suffixed 
                expando.Add(property.Key + Guid.NewGuid().ToString("N"), property.Value);
            } 
        }
        return expando as ExpandoObject;
    }

Sample usage, I have marked in bold the casting which gives us access in the example, I have marked the important bits with the ** letters:

  using (var transactionScope = new TransactionScope(TransactionScopeAsyncFlowOption.Enabled))
        {
            foreach (var dynamicParametersForItem in dynamicParametersForItems)
            {
                var idsAfterInsertion = (await connection.QueryAsync<object>(sql, dynamicParametersForItem)).ToList();
                if (idsAfterInsertion != null && idsAfterInsertion.Any())
                {
                    **var idAfterInsertionDict = (IDictionary<string, object>) ToExpandoObject(idsAfterInsertion.First());**
                    string firstColumnKey = columnKeys.Select(c => c.Key).First();
                    **object idAfterInsertionValue = idAfterInsertionDict[firstColumnKey];**
                    addedIds.Add(idAfterInsertionValue); //we do not support compound keys, only items with one key column. Perhaps later versions will return multiple ids per inserted row for compound keys, this must be tested.
                }
            }
        }

In my example, I look up a property value inside a dynamic object DapperRow and first convert the Dapper row into an ExpandoObject and cast it into a dictionary property bag as shown and mentioned in other answers here.

My sample code is the InsertMany method for Dapper extension I am working on, I wanted to grab hold of the multiple ids here after the batch insert.