Dynamic cast in c# in runtime

Question

I have 2 classes as you can see :

  static void Main(string[] args)
    {

        object m = (??????)"salam";
    }


public class A
{
    public string name { set; get; }
    public static implicit operator A(string _name)
    {
        A aa = new A();
        aa.name = _name;
        return aa;
    }
}
public class B
{
    public string family { set; get; }
    public static implicit operator B(string _family)
    {
        B bb = new B();
        bb.family = _family;
        return bb;
    }
}

I need to cast my string in runtime in this line :

object m = (??????)"salam";

Is there any solution to pass my class name as a string to cast my value .for example in runtime I need to cast "salam" to A or maybe B

The static cast is working good like this

 object m = (A)salam";
 object m = (B)"salam";

But I need to cast my string in runtime

Type x=null;
If(condition) 
x can be type of A
else 
x can be type of B

object m = (x)"salam";

https://stackoverflow.com/questions/11113259/how-to-call-custom-operator-with-reflection ? — Jeremy Lakeman, Jul 28 '20 at 05:31

Mahdi Tahsildari · Answer 1 · 2020-07-28T05:57:22.810

You need to use Interfaces for such a need. The following code shows how to do so.

To simulate your situtation, I wrote a method to return either A or B based on time. Here the list contains a bunch of objects which may be of Type A or B, depending on the second of execution. In the real-world scenario, you would get your types in various other ways.

public class StackOverflowQuestion
{
    public static void Run()
    {
        List<IBase> list = new List<IBase>();
        string types = "";
        for (int i = 0; i < 10; i++)
        {
            var randomType = GiveMeARandomIBaseType();
            System.Threading.Thread.Sleep(750);
            IBase hello = randomType.Convert("salam");
            list.Add(hello);
            types += hello.GetType().Name + ",";
        }

        types = types.Trim(',');
        //sample result : B,B,A,B,A,A,B,A,B,B
    }

    static IBase GiveMeARandomIBaseType() {
        if (DateTime.Now.Second % 2 == 0)
            return new A();
        else
            return new B();
    }
}

public interface IBase {
    public IBase Convert(string s);
}
public static class MyExtensions {
    public static T Convert<T>(this string str, IBase b) where T : IBase {
        try
        {
            return (T)b.Convert(str);
        }
        catch (Exception)
        {
            return default;
        } 
    }
}
public class A : IBase
{
    public IBase Convert(string s) {
        return (A)s;
    }
    public string name { set; get; }

    public static implicit operator A(string _name)
    {
        A aa = new A();
        aa.name = _name;
        return aa;
    }
}
public class B : IBase
{

    public IBase Convert(string s)
    {
        return (B)s;
    }
    public string family { set; get; }
    public static implicit operator B(string _family)
    {
        B bb = new B();
        bb.family = _family;
        return bb;
    }
}

Thanks Mahdi .I know that ,But I need to cast in runtime .I mean in some conditions my casting class can be A or sometimes can be B based on some situations in my application . — Ehsan Akbar, Jul 28 '20 at 05:19
OMG!!! this answer literally saved my life. thank you so much. it should be the accepted answer. @MahdiTahsildari — Moslem Hadi, Jul 29 '20 at 06:24

score 0 · Answer 2 · answered Jul 29 '20 at 18:03

I had a similar problem and after all the study and time, I was able to approach the desired result in the following way. I used an internal method to access (the inside of) the class and this method returns the cast desired result.

Step 1: in class

public class A
    {
       public string Name { set; get; }

        public static implicit operator A(string name)
        {
            return new A
            {
                Name = name
            };
        }

        public A GetCasting(object a)
        {
            A i = (A)a;
            return i;
        }
    }

    public class B
    {
        public string Family { set; get; }

        public static implicit operator B(string family)
        {
            return new B
            {
                Family = family
            };
        }
        public B GetCasting(object b)
        {
            B i = (B)b;
            return i;
        }
    }

Step 2: in controller or code

    var className = "A";
    var classMethod = "GetCasting";
    var classType = Assembly.GetExecutingAssembly().GetTypes().Where(t => t.IsClass && t.Name == className).FirstOrDefault();
    var classInstance = Activator.CreateInstance(classType);
    var castMethod = classType.GetMethod(classMethod);
    var yourObject = "salam";
    var objectData = new object[] { yourObject };
    var resultObject = castMethod.Invoke(classInstance, objectData);

Hi AmirHussein. Although it works, using reflection is not a good choice, because one might forget to add the proper method for the class. This approach is prone to exceptions because the compiler tries calling the method whether it exists or not. Using an interface prevents you from facing an exception in run-time. Instead, if your class lacks the proper method, you will be warned before compile. — Mahdi Tahsildari, Jul 30 '20 at 05:27

Dynamic cast in c# in runtime

2 Answers2