How do I cast object to dictionary?

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1.00/5 (1 vote)

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How do i cast an object to dictionary?

The dictionary key & value can be any type.

What I have tried:

C#

public class Example {

    void CallMethod () {
        SomeMethod (new Dictionary<string, bool> ());
        SomeMethod (new Dictionary<int, long> ());
        SomeMethod<Dictionary<string, bool>> (new Dictionary<string, bool> ());
    }
    
    void SomeMethod (object value) {
        var dic = value as Dictionary<,>;
        // What is type of Dictionary key or value?
    }

    void SomeMethd<T> (T value) {
        // T can be Dictionary, int, bool, List, ...
        if (value is Dictionary) {
            // T is dictionary, but we don't know type of key and value
            // How do i cast it to dictionary?
            var dic = value as Dictionary<,>;
            foreach (var item in dic) {
                
            }
        }
    }

    T SomeMethod<T> () {
        // I want to load the dictionary here
        if (typeof(T) is IDictionary) {
            // Now, what is type of the key and value?
            IDictionary dic = new Dictionary<,> ();
            int count = 1;
            for (int i = 0; i < count; i++) {
                dic.Add (SomeMethod<Type of Key> (), SomeMethod<Type of value> ());
            }
            // Throws an exception
            return dic;
        }
        return default(T);
    }
    
}

Posted 22-Jul-17 0:00am

EmpireWorld

Updated 2-Mar-23 22:37pm

v3

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Mehdi Gholam 22-Jul-17 6:08am

What do you intend to do in SomeMethod() ?

EmpireWorld 22-Jul-17 6:12am

I want to write the object using BinaryWriter.

3 solutions

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OriginalGriff · Answer 1 · 2017-07-22T00:19:00

Solution 2

Unless you know the type of the dictionary - and that means key and value - the only way to do it is to cast it to a Dictionary<object, object> - which is a very bad idea as it gets rid of the strong typing which makes C# so robust. At this point you are relying on runtime-casts to use the dictionary you create, and that's a poor idea.

Have you instead considered using Generics, so you don't have to cast your Dictionary, the types are inferred when you call the method?

void SomeMethod<K, V>(Dictionary<K, V> dict)
    {
    ///...
    }

It'll make your code both more robust, and a lot easier to read.

Posted 22-Jul-17 0:19am

OriginalGriff

Comments

EmpireWorld 22-Jul-17 6:27am

I need a method that takes only one generic type and one argument, that accepts Primitive Types, Generic Types such as Collections, List, Dictionary and Custom classes. So how do i do it while you say to make overload for dictionary?

OriginalGriff 22-Jul-17 6:49am

Because the properties and methods available are different, I'd produce overloads that take generics:
void SomeMethod<K, V>(Dictionary<K, V> dict)
{
///...
}
void SomeMethod<t>(List<t> list)
{
}
void SomeMethod<t>(IEnumerable<t> enumerable)
{
}
You can add other parameters to those as required.

EmpireWorld 22-Jul-17 7:01am

Please check the T SomeMethod<t> (); in the question, i need a recursive method.

OriginalGriff 22-Jul-17 7:09am

Don't: create a method which accepts a generic dictionary<K, V> and K is the type of the key, and V is the type of the Value. You can use those inside the method to create new instances, or whatever you need.

What are you trying to achieve? You seem to be overcomplicating things here.

EmpireWorld 22-Jul-17 7:12am

I am trying to make a Save and Load solution.

I want to be able to save everything such as Dictionaries, Custom Classes, ...

What i have is a single Save and Load method.

Save<t> (T value);

and

Load<t> ();

I need a recursive save and load functionally for both.

How do i achieve this?

OriginalGriff 22-Jul-17 7:23am

Ah - right.
Don't roll your own - there are existing solutions which do this already, and in a handily portable way. Have you considered using JSON?
This may help:
https://www.codeproject.com/Articles/272335/JSON-Serialization-and-Deserialization-in-ASP-NET
Google will find you loads of examples which will do the job for you already!

EmpireWorld 22-Jul-17 7:27am

I want to do it using Binary. How do i achieve this?

Also the Dictionary<string, bool> can be Dictionary<Dictionary<string, int>, bool>, what do i do when the dictionaries are nested?

How do i get type of key and value of the dictionary from T?

OriginalGriff 22-Jul-17 7:49am

That's why "brew your own" is such a pain in the but - you have to cope with everything without knowing anything about what you are serialising, which makes it very complicated indeed.
Why binary specifically? If it's a "human readable" thing, then JSON or XML streams and an encrypted container will do it better, and if it's a space thing then JSON / XML and a ZIP container might work well.
If it's because you really, really like testing edge cases and spending a few weeks fixing the bugs, then this may help you get started:
https://www.codeproject.com/Articles/15646/A-Deep-XmlSerializer-Supporting-Complex-Classes-En
It's worth a read as background to what you are trying to do yourself, even if you don't use any of the code.

EmpireWorld 22-Jul-17 7:55am

How Json.NET serializes objects?

There is no difference what you pass in, it just serializes it.

So how can do same thing? How Json.Net does it?

OriginalGriff 22-Jul-17 7:58am

With some very complicated software! :laugh:
That's why I suggested it - it's proven code you can "just use" and the results are nicely portable if you need multiple apps accessing the data.

EmpireWorld 22-Jul-17 8:00am

Thanks, but i need to do it myself, could you explain how JSON.net achieved it?

OriginalGriff 22-Jul-17 8:10am

Not in the kind of detail you'd need - I didn't write JSON so I don't know it's internals.
I'd imaging it uses reflection in the same way the last page I linked to does.

Mehdi Gholam · Answer 2 · 2017-07-22T00:24:00

Solution 3

Depending on how much the type information is important to you within the SomeMethod() method you can do:

C#

// minimal type info needed
void SomeMethod (System.Collections.IDictionary dictionary)
{
   foreach(var k in dictionary.Keys)
   {
      // k and dictionary[k] as value
   }
}

Or if the types are needed:

C#

// overloaded for each case
void SomeMethod (System.Collections.Generic.Dictionary<int,long> dictionary)
{
   foreach(var kv in dictionary)
   {
      //access to kv.Key and kv.Value as int and long
   }
}

void SomeMethod (System.Collections.Generic.Dictionary<string,bool> dictionary)
{
   foreach(var kv in dictionary)
   {
      //access to kv.Key and kv.Value as string and bool
   }
}

Posted 22-Jul-17 0:24am

Mehdi Gholam

Updated 22-Jul-17 0:35am

v2

Comments

EmpireWorld 22-Jul-17 6:30am

I need a method that takes only one generic type and one argument, that accepts Primitive Types, Generic Types such as Collections, List, Dictionary and Custom classes.
Also i don't have access to kv.Key or kv.Value. (please try your script)

Mehdi Gholam 22-Jul-17 6:35am

Sorry, fixed.

EmpireWorld 22-Jul-17 6:38am

What is the type of k? is it object?

As i checked it is object.

Nice, Thanks, it works as well.

Your first example is the solution.

i tried it:

        void Method ( object value )	{		IDictionary dic = value as IDictionary;		foreach ( var item in dic.Keys )		{			Debug.Log ( item );			Debug.Log ( dic [ item ] );		}	}

But there is no need to use IDictionary type as argument just replace it with object. and i will accept your solution.

Mehdi Gholam 22-Jul-17 6:40am

Yes

EmpireWorld 22-Jul-17 6:46am

Your first example is the solution. please update it and make it like my question. i will accept your question.

Mehdi Gholam 22-Jul-17 6:51am

I would keep the IDictionary since the compiler will help you with an error if you pass any thing else.

EmpireWorld 22-Jul-17 7:01am

Please check the T SomeMethod<t> (); in the question, i need a recursive method.

Satya Prakash Swain · Answer 3 · 2017-07-22T00:09:00

Solution 1

Hope, i got the question correctly. Object to Dictonary. It runs without error.

var dic = value as Dictionary<object,object>;

Posted 22-Jul-17 0:09am

Satya Prakash Swain

Comments

EmpireWorld 22-Jul-17 6:13am

How do i get the dictionary key type? in your code the type of the key and value both are object there is no difference?!