My HTTP response data includes a field that is structured as a Dictionary<string,object>. Accessing the Object in debug mode shows me what I expect to see, i.e.
ValueKind = Object:
{ "someProp" : "someValue",
"anotherProp" : "anotherValue" .. }
=> the object therefore contains the large json formatted data that I need to access. However, I can't figure out how to do that .. The commonly suggested method returns null:
var myValue = Odata.GetType().GetProperty("someProp").GetValue(Odata, null);
which makes me think there is something I should be serializing which I am not and regardless how much I tried, I can't find any methods to work.
Here is some more info, if it is not enough I will add whatever is needed. I broke it down a lot to try to show clearly what I am getting each step):
// assume Odata = the Object value from the dictionary
//perform reflection
var type = Odata.GetType() // this gives System.Text.json.JsonElement
//get type properties at runtime
var props = type.GetProperties()
//returns array of 2 :
//System.Text.Json.ValueKind and System.Text.json.JsonElement
//attempting to access my properties in the JsonElement
var someValue= type.GetProperty("someProp").GetValue(Odata,null) //this gives null
I don't necessarily want an exact solution, but pointing me to the right place to read would also be very useful!
When you do GetType().GetProperty() you're using the GetProperty() method from Type class, you're using reflection. You want to use the GetProperty method of JsonElement class instead:
var myValue = Odata.GetProperty("someProp").GetString();
Related
I'm writing a compare properties two objects of some class, for further listing differences.
Class oldObj, newObj;
//some initiation of above
Class classObject = new Class();
var objectKeys = classObject .GetType().GetProperties().ToList();
objectKeys.ForEach(key => {
var previousKeyValue = key.GetValue(oldObj);
var newKeyValue = key.GetValue(newObj);
if (!Equals) {...}
});
In special cases, newObj or oldObj can be nulls.
My problem is that, in such a case: key.GetValue(null) I'm getting CS0120 exception - "Non-static method requires a target".
Looking at PropertyInfo options (from metadata):
public object? GetValue(object? obj);
I assumed that it will be able to handle such a situation with object being null, with e.g. return null as its value.
Could you please explain if this is proper behaviour of this code, or I'm making something wrong to use null?
In such a case I would probably just before ForEach make some verification if objects are nulls and write separate compare code, handling this situation.
You are misunderstanding the nature of the parameter that is passed to GetValue().
When you pass in an object reference, it means that the reference is an instance property on an instance of an object. If you omit the object reference, you are telling the reflection api that you are trying to access a static member.
Story
I'm trying to write a generic method which combines property names, types and content value to generate a unique string for the value held by the object passed.
The idea is to generate a unique SHA3-512 Hash based on the generated string sequence which can be used to compare objects on generic bases by looking at their content.
Example
Let's say we have a class like this ...
class MyClass {
private Int32 Id = 5;
public String Name = "some string";
protected DateTime CreateDate = DateTime.Parse("2017-08-21 15:00:07");
}
... and the mentioned method to generate the unique string
static String GetContentString<T>(T obj) where T : class {
...
}
In theory this should work somewhat like this:
var myObj = new MyClass();
var uniqueContentString = GetContentString(myObj);
Console.WriteLine(uniqueContentString);
>>> Id:Int32:5$Name:String:some string$CreateDate:DateTime:2017-08-21 15:00:07
Problem
I'm having difficulties building the GetContentString Method. This is what I have already:
Object obj = ... // given object
Type type = obj.GetType();
IList<PropertyInfo> propertyInfos = type.GetProperties().Where(x => x.CanRead).ToList(); // Marker #2
StringBuilder sb = new StringBuilder();
foreach (PropertyInfo pi in propertyInfos)
{
sb.Append(pi.Name);
sb.Append(":");
sb.Append(pi.PropertyType.Name);
sb.Append(":");
sb.Append(pi.GetValue(obj) ?? "[ISNULL]"); // Marker #1
sb.Append(":");
}
return sb.ToString();
I tried running the method for a few different types of values like "some string" or 1234 (Int32) and ran into a few issues.
Given a string, the method call throws an exception of type System.Reflection.TargetParameterCountException and the message Parameter count mismatch at #1. I found out that an optional index can be passed to an overloaded version of pi.GetValue(..) which then returns one of the single letters. But how do you know when to stop? If you call an index which doesn't exist it throwns an exception of the type System.Reflection.TargetInvocationException. How do you get the value of a string object using reflection?
Given an integer value, the method call doesn't find any properties at #2. Which brings up the question of how to get the value of an integer object using reflection?
And also some general questions; do you guys think this is a good approach to get a unique string? Is reflection the way to go here? Is it even possible to write a generic solution to this problem?
Without looking at reflection, how about JSON serialization with something that .net framework is able to ?
Reflection isn't something extremely fast and you'll run into issues at the first unhandled exception.
Then, you should do that recursivly if your objects can contains complex properties, wich is not a problem with json serialization !
I want to get all properties from json that StartsWith particular text
dynamic results = JsonConvert.DeserializeObject<dynamic>(json);
So now below is what i get in results
{"abc" : "Text", "abcde" : "Text2","prop" : "myprop"}
Is it possible to do something like
results.Where(x => x.StartsWith("abc"))
You could simply use results.GetType().GetProperties(), which will give you an array of properties present in the deserialized JSON object.
You could then iterate over that array to get the PropertyInfo objects whose Name starts with whatever string you want, and call GetValue() to obtain the properties' values of interest.
Or you simply don't deserialize at all, but parse the object and treat it as JSON:
var jObject = JObject.Parse(jsonString);
foreach (var rootProperty in jObject)
{
if (rootProperty.Key.StartsWith("whatever"))
{
var valueOfInterest = rootProperty.Value;
}
}
Simply retrieve the runtime-type of the result-object and query its properties using Type.GetProperties:
var type = results.GetType();
type.GetProperties().Where(x => x.Name.StartsWith("abc"));
EDIT: Because any method called on an instance of dynamic is dynamic as well, you have to cast the result of results.GetType into Type. Otherwise you´ll get a compiler-err stating that you can´t use an anonymous method on a dynamically bound operation.
var type = (Type)results.GetType();
I have a function that returns an anonymous type like so (simplified for illustrative purposes)...
public object GetPropertyInfo()
{
return new {
PropertyName = "Foo",
Value = "Laa"
};
}
When I do this...
dynamic pi = GetPropertyInfo();
Console.WriteLine(pi);
It outputs this (the same as if I did '?pi' in the immediate window)...
{ PropertyName = "A", Value = 44 }
PropertyName: "A"
Value: 44
But if I try doing this...
string propertyName = pi.PropertyName;
...it compiles but throws a runtime exception saying
Exception thrown: 'Microsoft.CSharp.RuntimeBinder.RuntimeBinderException' in System.Core.dll
Additional information: 'object' does not contain a definition for 'PropertyName'
What gives? What am I missing here?
The problem is that anonymous types are internal, which means that you can't access their properties with dynamic property accessors from projects other than the one they were created in. The dynamic binding treats them as the closest public inherited type it knows about--object.
To fix this, you can declare a public type to represent the values you're expecting to find in your anonymous type. This is probably a good idea anyway, since you're clearly expecting to consume the returned properties in other parts of your code. Using a declared type also enables you to maintain type-safety, avoiding the need for dynamic entirely.
If you absolutely must use dynamics here, the next best option is probably to change your AssemblyInfo.cs file to make internal properties accessible to the project you're trying to access them from:
[assembly:InternalsVisibleTo("MyOtherProject")]
Edit
According to your edit. Apparently you are not required dynamic at all as there are no dynamic properties. Just create a concrete type with your predefined properties. It's better to avoid dynamic when possible anyway.
Old Answer
You need to use an ExpandoObject. Reference here.
In fact, GetPropertyInfo() should return an ExpandoObject.
dynamic foo = this.GetPropertyInfo();
string i = foo.MyPropertyName;
private ExpandoObject GetPropertyInfo()
{
dynamic obj = new ExpandoObject();
obj.PropertyName = "MyPropertyName";
obj.PropertyType = "MyPropertyType";
return obj;
}
The ExpandoObject class enables you to add and delete members of its
instances at run time and also to set and get values of these members.
This class supports dynamic binding, which enables you to use standard
syntax like sampleObject.sampleMember instead of more complex syntax
like sampleObject.GetAttribute("sampleMember").
Also, you can use System.Reflection
object D = GetPropertyInfo();
Type t = D.GetType(); // get object's type
PropertyInfo p = t.GetProperty("PropertyName"); // look up for the property:
object P = p.GetValue(D, null); // get the value
Fiddle demo
I'm trying to do is deserialize json into an object in c#. What I want to be able to do is pass any object get it's type and deserialize the json into that particular object using the JSON.Net library. Here are the lines of code.
Object someObject1 = someObject;
string result = await content.ReadAsStringAsync();
return JsonConvert.DeserializeObject<someObject1.GetType()>(result);
The last line throws an exception of
operator '<' cannot be applied to operands of type 'method group'
How do I get the data type in the <> without c# complaining. What do I have to do to make this code work? And what knowledge am I missing?
JsonConvert.DeserializeObject<T> needs a compile-time type. You can't pass it a type in run time as you want to do in question (nothing different than declaring a List<T>). You should either deserialize to a generic json object JObject (or to dynamic) or you should create an instance of an object and fill it with json.
You can use the static method PopulateObject (of course if your object's properties match the json you want to deserialize).
JsonConvert.PopulateObject(result, someObject1 );
You can ignore the generic method and use dynamic:
var myObj = (dynamic)JsonConvert.DeserializeObject(result);
However, if the objects aren't of the same type you'll have a hard time distinguishing between the types and probably hit runtime errors.
For anyone bumping into this problem, the newer versions of Newtonsoft JSON have an overload that takes a type as a second argument and where you can pass a dynamic value without jumping through any hoops:
var myObj = JsonConvert.DeserializeObject(string serializedObject, Type deserializedType);
This is the best way to populate an object's fields given JSON data.
This code belongs in the object itself as a method.
public void PopulateFields(string jsonData)
{
var jsonGraph = JObject.Parse(jsonData);
foreach (var prop in this.GetType().GetProperties())
{
try
{
prop.SetValue(this, fields[prop.Name].ToObject(prop.PropertyType), null);
}
catch (Exception e)
{
// deal with the fact that the given
// json does not contain that property
}
}