casting at runtime in c#

prasadbuddhika

hi , I got an object which is a generic, at runtime i pass the type for T and create the proper object. the generic object as follows

class parent {
string name;
T childObject;
}

I create the parent in runtime using the reflection , for e.g.

Type type = x;
Dynamic response = Activator.CreateInstance(typeof(parent<>).MakeGenericType(type));

it works fine , but the problem is when I try to assign an object to response.childObject it gives me an exception saying that i'm missing cast and it cannot implicitly cast the object. the object try to assign is also created using reflection, ADDED LATER: I'm not sure this part will be important for this issue , but anyway , the object i'm trying to assign to response.childObject is also an object created by deserialization , means for in order to deserialize this object i have to give the type , so that type also crated using reflection in a similar way described above. i would really appreciate your help on this. thanks in advance.

Simon_Whale

I dont know how it actual works if I am honest (as I found the question interesting) but my modifying your code to this

Type t = typeof(Parent<>);
int y = 1234;
Type type = y.GetType();

dynamic response = Activator.CreateInstance(t.MakeGenericType(type));
response.MyValue = 123;

public class Parent
{
public string name = string.Empty;
public T MyValue;
}

I was able to assign a value to the property MyValue. *Edit* Not sure if it helps but I've just read through this MSDN article on Type.MakeGenericType[^], I found this an interesting Question :-D

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prasadbuddhika

thanks , I also tried the value types and it works , but the problem came when i'm trying to assign reference type.

Simon_Whale

Type t = typeof(Parent<>);
Type type = typeof(Data);

dynamic response = Activator.CreateInstance(t.MakeGenericType(type));
Data es = new Data() { Name = "Fred", value = 213 };
response.value = es;

public class Parent
{
public string name = string.Empty;
public T value;
}

public class Data
{
    public string Name = string.Empty;
    public int value = 0;
}

I have also tried it with the following and it still works can you expand your problem with some sample code? or a snippet?

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Simon_Whale

Your welcome :-D

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prasadbuddhika

Thanks again , ok then I think I have to focus on the deserialzed object , unfortunately i haven't got the code snippet right now , but I will definitely post that code snippet soon. thanks .

prasadbuddhika

hi , this is how i'm doing the deserialization

Type genericSyncObj = typeof(SyncObject<>);
Type syncObj = genericSyncObj.MakeGenericType(type);
IList customObjectList = (IList)Activator.CreateInstance((typeof(List<>).MakeGenericType(type)));

foreach (string value in pullRequest.Knowledge)
{
dynamic syncObject = JasonSerializer.Deserialize(value, syncObj, null);
customObjectList.Add(syncObject.Object);
}

and i'm getting the exception at here

dynamic responseSync = Activator.CreateInstance(typeof(SyncObject<>).MakeGenericType(type));
responseSync.Object = customObjectList[y] ;

thanks .

Simon_Whale

The problem is that customObject[y] is returned as an object which is why it fails. if you then hard code a cast such as for example.

//assume SomeTestClass is the type of class that you are using
//Type type = typeof(SomeTestClass);
responseSync.Object = (SomeTestClass)customObject[y];

it works as you need it to do, but how to create this as a generic routine I'm not sure at the moment as (typeof(SomeTestClass))customObject[y] or even (typeof(SomeTestClass))CustomObject[y] is rejected by the compiler.

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prasadbuddhika

thanks , yes this is the place where i'm stuck , need to cast in runtime , if you find a way please share it .

Simon_Whale

//Create sample data in the same method as OP
IList datalist = (IList)Activator.CreateInstance(typeof(List<>).MakeGenericType(typeof(Data)));

datalist.Add(new Data {Name = "SIMON", value = 1});
datalist.Add(new Data {Name = "SIMON", value = 2});
datalist.Add(new Data {Name = "SIMON", value = 3});

//Create the destination object that is declared using
//the dynamic keyword
Type t = typeof(Parent<>);
Type type = typeof(Data);

dynamic response = Activator.CreateInstance(t.MakeGenericType(type));

//************ possible work around not sure if it would be a correct way
//************ but it works.

Type SingleRecordType = datalist[0].GetType();
dynamic Destination = Activator.CreateInstance(SingleRecordType);
Desintation = datalist[0];

//Add the record to the response object
response.value = Desintation;

have a look at this. it is a bit of a work around converting the list item from object to a specific type at runtime. Thanks Simon **edit** missed a GetType()

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BobJanova

If you're getting a runtime exception, then it's probably because the object actually isn't of the right type. The exception message should tell you what it is and what it's trying to cast it to.

prasadbuddhika

hi thanks it seems to be working, though it is a workaround . thanks for the clue . ** yes i noticed that and i fixed it by calling the GetType() thanks.

prasadbuddhika

hi , yes , that's the case , I was searching for a way to solve this at runtime. anyway I got a clue a from Simon_Whale. thanks.