I'd like to access the value of a dynamic c# property with a string:
dynamic d = new { value1 = "some", value2 = "random", value3 = "value" };
How can I get the value of d.value2 ("random") if I only have "value2" as a string? In javascript, I could do d["value2"] to access the value ("random"), but I'm not sure how to do this with c# and reflection. The closest I've come is this:
d.GetType().GetProperty("value2") ... but I don't know how to get the actual value from that.
As always, thanks for your help!
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)
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>;
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)
{
}
}
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
In .Net core 3.1 you can try like this
d?.value2 , d?.value3
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<string, object>. 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.
Use dynamic with Newtonsoft.Json.JsonConvert.DeserializeObject:
// Get JSON string of object
var obj = new { value1 = "some", value2 = "random", value3 = "value" };
var jsonString = JsonConvert.SerializeObject(obj);
// Use dynamic with JsonConvert.DeserializeObject
dynamic d = JsonConvert.DeserializeObject(jsonString);
// output = "some"
Console.WriteLine(d["value1"]);
Sample:
https://dotnetfiddle.net/XGBLU1
Related
I have a library that is doing a bunch of reflection work relying on the PropertyInfo of the classes it receives (to get and set values).
Now I want to be able to work with dynamic objects, but I can't find how to get the PropertyInfo of a dynamic's properties. I've checked the alternatives, but for those I'd need to change everywhere I use PropertyInfo to get/set values.
dynamic entity = new ExpandoObject();
entity.MyID = 1;
// - Always null
PropertyInfo p = entity.GetType().GetProperty("MyID");
// - Always null
PropertyInfo[] ps = entity.GetType().GetProperties();
// - These are called everywhere in the code
object value = p.GetValue(entity);
p.SetValue(entity, value);
Is it possible to get or create a PropertyInfo somehow just to be able to use it's GetValue() and SetValue() on a dynamic object?
Under the covers an ExpandoObject is really just a dictionary. You can get at the dictionary just by casting it.
dynamic entity = new ExpandoObject();
entity.MyID = 1;
if(entity.GetType() == typeof(ExpandoObject))
{
Console.WriteLine("I'm dynamic, use the dictionary");
var dictionary = (IDictionary<string, object>)entity;
}
else
{
Console.WriteLine("Not dynamic, use reflection");
}
You could modify your Mapping method to check if the object being passed in is dynamic and route through a different path that just iterates over the keys of the dictionary.
https://dotnetfiddle.net/VQQZdy
I have a project in which I have some assemblies which implement an abstract class.
Each assembly has a public enum called ResultEnum.
This ResultEnum's value is stored in a database as an int.
I have another web project which displays some info, and I want it to also display this int's string representation - the name of the corresponding value from the ResultEnum.
What I want to do is, using MEF, load all the relevant assemblies (no problem here), search for this enum using reflection (no problem here also) and then to store the enum in some way, and cache it in order to avoid all this process the next time I want to convert the int from the database to the string representation (and the other way around if necessary) since I have several thousands of records in my db table.
AggregateCatalog catalog = new AggregateCatalog();
catalog.Catalogs.Add(new DirectoryCatalog(path));
_container = new CompositionContainer(catalog);
try
{
_container.ComposeParts(this);
}
catch (CompositionException compositionException)
{
Console.WriteLine(compositionException.ToString());
}
foreach (var task in myTasks)
{
TaskAbstract instance = (TaskAbstract)task.CreateExport().Value;
MemberInfo[] infos = instance.GetType().GetMembers(BindingFlags.Public | BindingFlags.Static);
foreach (MemberInfo member in infos.Where(x => x.Name.Equals("ResultEnum")))
{
Console.WriteLine(member);
}
}
What do you suggest the next move should be?
How should I store/cache it?
Thanks
In addition to #Thomas's answer:
As using reflection you can get exact int value from a property, the name for that concrete value could be gotten using the next expression:
var enumValueName = Enum.GetName(member.GetType(), member.GetValue(instance));
UPD
I really missed that you reflect MemberInfos. To apply my solution you can update you reflection this way:
foreach (var task in myTasks)
{
TaskAbstract instance = (TaskAbstract)task.CreateExport().Value;
// Reflect properties, not all members
PropertyInfo[] infos = instance.GetType().GetProperties(BindingFlags.Public | BindingFlags.Static);
foreach (PropertyInfo prop in infos.Where(x => x.Name.Equals("ResultEnum")))
{
var enumValueName = Enum.GetName(prop.GetType(), prop.GetValue(instance));
}
}
Or you could cast MemberInfo to PropertyInfo.
One approach to solving this problem is to consider using a subclassable enums technique (also sometimes referred to as a polymorphic enum).
I wrote a couple of generic classes specifically to support these kinds of types which you can read about here. Also, a proposal has been submitted to the Roslyn compiler team on Github to add support for these types of enums to C#.
Here is an example of a set of subclassable enums that have two underlying types, string and integer, using the classes from my project:
public sealed class Status : StringIntegerEnum<Status>
{
public static readonly Status Active = new Status("active", 1);
public static readonly Status Inactive = new Status("inactive", 0);
private Status(string status, int statusCode) : base(status, statusCode) {}
}
Note that the string value is not the same as the constant name itself, which allows you to have underlying string values with characters that violate the normal naming conventions in C#.
The StringIntegerEnum<tStringIntegerEnum> base class provides .AllValues, .AllNaturalValues and .AllStringValues static methods that you can use to enumerate the list of enum values or both types of their underlying values.
From your comment:
I agree, But question is how do I iterate over the values and names of the enumerator
I assume you mean "enumeration", not "enumerator". You can use the Enum.GetValues method:
var valuesToNames =
Enum.GetValues(enumType)
.Cast<object>()
.ToDictionary(o => (int)o, o => Enum.GetName(enumType, o));
And, is there a better solution than a dictionary
Better how? I think a dictionary is a fine solution; is there any reason why you would want something else?
This is how i've written the code eventually:
resultEnumsForTasks = new Dictionary<string, Dictionary<UInt16, string>>();
foreach (var task in myTasks)
{
Dictionary<UInt16, string> _enum = new Dictionary<UInt16,string>();
TaskAbstract instance = (TaskAbstract)task.CreateExport().Value;
MemberInfo resultEnum = instance.GetType().GetMember("ResultEnum").FirstOrDefault();
if (resultEnum == null)
continue;
string[] names = Enum.GetNames(resultEnum as Type);
IList<int> vals = (IList<int>)Enum.GetValues(resultEnum as Type);
for (int i = 0; i < names.Length; i++)
{
_enum.Add(Convert.ToUInt16(vals[i]), names[i]);
}
resultEnumsForTasks.Add(instance.GetType().Name, _enum);
}
It's very similar to #n.turakulov 's solution, however his solution didn't work for me since I got an empty list of PropertyInfo for some reason...
Thanks for everyone who assisted!
A dynamic object is generated using a Json deserializing component (Jil) I am using, and I am able to access the properties directly. But I don't know their names in advance, so I am trying to get the names with reflection. I tried doing this:
var props = myDynObj.GetType().GetProperties();
but the page times out. Doesn't give me anything in debugger, just sits there doing nothing, or something and not telling me.
This even happens when I even do this:
var t = myDynObj.GetType();
But when I do this, it works:
var val = myDynObj.MyStaticValue1
Just can't really do anything else with it. Anyonw know why, and how I can get this to work?
Please allow me to note:
Before I get started, if you don't know the members already when you're parsing JSON, you should not be parsing into a dynamic object. The built-in .Net JavaScriptConverter class can parse JSON into a IDictionary<string, object> which would be much better for you.
However, if you still want to use dynamic objects for some reason:
If you want to stick with your current library: I dont know how exactly that class is working, and I'm not saying this is the best solution, but by looking at the source it jumps out to me that you can grab a list of the ObjectMembers keys using reflection.
Type t = typeof(JsonObject)
var fi = t.GetField("ObjectMembers", BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
IEnumerable<string> keys = ((Dictionary<string, JsonObject>)fi.GetValue(obj)).Keys;
Edit: Seeing that JsonObject implements IDynamicMetaObjectProvider, the following method mentioned in this question will also work on it:
public static IEnumerable<string> GetMemberNames(object target, bool dynamicOnly = false)
{
var tList = new List<string>();
if (!dynamicOnly)
{
tList.AddRange(target.GetType().GetProperties().Select(it => it.Name));
}
var tTarget = target as IDynamicMetaObjectProvider;
if (tTarget !=null)
{
tList.AddRange(tTarget.GetMetaObject(Expression.Constant(tTarget)).GetDynamicMemberNames());
}else
{
if (ComObjectType != null && ComObjectType.IsInstanceOfType(target) && ComBinder.IsAvailable)
{
tList.AddRange(ComBinder.GetDynamicDataMemberNames(target));
}
}
return tList;
}
If you are open to trying a different JSON converter: try this class here: http://pastie.org/private/vhwfvz0pg06zmjqirtlxa I'm not sure where I found it (I can't take credit) but here is an example of how to use it how you want:
// Create dynamic object from JSON string
dynamic obj = DynamicJsonConverter.CreateSerializer().Deserialize("JSON STRING", typeof(object));
// Get json value
string str = obj.someValue;
// Get list of members
IEnumerable<string> members = (IDictionary<string, object>)obj).Keys
Personally I like using the second one, it is simple and easy to use - and builds off of the built in .Net JSON parser.
I have a System.object type list.
I can't use [0] or [1],... to get value because it is object.
I tried GetType() and use many functions, but didn't work.
Is there any way to read it?
I write a function can convert any object, convert means validate or something.
private static IDictionary<string, object> objectConvert(object data)
{
var result = new Dictionary<string, object>();
var attrs = data.GetType().GetProperties();
foreach (var attr in attrs)
{
// if attribute is object do something (use use recursion )...
// if attribute is list do something (use recursion)...
// if not object or list, just add to result
// after all return result
}
}
Attribute is object I work well, but when it is list I tried so hard but can't get any element in list object.
You can cast it. Use as so that it is null if the cast fails and check it:
var list = yourObjectInstance as IList<type_here>();
if (list != null) {
// cast successful.
}
If you know the actual type of your object, simply cast it to that type using standard casting. You can then use indexer on it like ((List<T>)YourObject)[0].
I had the cunning idea of using a dynamic variable to test the results of a method that returns an anonymous type - more specifically it returns a JsonResult, which as json looks like this
{ "newData" : [ 1120741.2697475906,
826527.64681837813
],
"oldData" : [ 1849870.2326665826,
1763440.5884212805
],
"timeSteps" : [ 0,
4.8828124999999998e-10
],
"total" : 2
}
I can read the JSonResult which will give me the anonymous type. Here's my code:
var jsonResult = controller.GetChangeData(1) as JsonResult;
dynamic data = jsonResult.Data;
Assert.AreEqual(2, data.total); // This works fine :)
But how do I get at "newData" for example? This code....
var newData = data.newData;
Gives me a System.Linq.Enumerable.WhereSelectArrayIterator, but I don't know what to do with it to be able to just use it as an arry of doubles.
I tried casting it as a double[], but it doesn't work either.
As an aside, can I easily check if a property is defined on the dynamic?
The reason .ToArray() doesn't work is that it's an extension method, and extension methods aren't available at runtime. That just means you have to call the function statically. Does Enumerable.ToArray<double>(data.newData) work?
You may need Enumerable.ToArray(Enumerable.Cast<double>(data.newData)) depending on what elements newData actually has.
To get the properties of an instance of a dynamic type
PropertyDescriptorCollection props = TypeDescriptor.GetProperties(dyn);
foreach (PropertyDescriptor prop in props)
{
object val = prop.GetValue(dyn);
var propName = prop.Name;
var propValue = val;
}
where dyn is an instance of a dynamic object.
Could you use the JavaScriptSerializer class to parse the Json string into a dynamic variable? Eg:
var serializer = new JavaScriptSerializer();
var jsonObj = serializer.Deserialize<dynamic>(jsonString);
var newData1 = jsonObj["newData"][0];