C# Merge 2 objects of the same with linq 2 object

Question

public class SomePropertyClass{
    public string VarA{get;set;}
    public string VarB{get;set;}
}

SomePropertyClass v1 = new SomePropertyClass(){VarA = "item 1"};
SomePropertyClass v2 = new SomePropertyClass(){VarB = "item 2"};

Is it possible to create a third variable that will have:

v3: VarA = "item 1",VarB = "item 2"

I mean, I want to merge objects with linq to object.

Edit
for now i need from the same type. but it would be nice in the future to merge by property name.

I have an account model with a lot of properties that the user input in step 1.
I want to merge this half full model with step 2 half full model.

Edit 2

//step 1
        GlobalOnBoardingDataModel step1= (GlobalOnBoardingDataModel)HttpContext.Current.Session[SessionVariableNameStepOne];
//step 2           
        GlobalOnBoardingDataModel step2 = (GlobalOnBoardingDataModel)HttpContext.Current.Session[SessionVariableNameStepTwo];



     class GlobalOnBoardingDataModel {
        public string Email;//step 1
        public string Name;//step 1
        public string Phone;//step2
        public string Address;//step2
        }
    }

thanks

var v3 = new SomePropertyClass { VarA = v1.VarA, VarB = v2.VarB }; ? Why would you want to use LINQ ? — user703016
– user703016, Commented Jan 26, 2012 at 8:18
Help us understand more about your use case. Will you always have exactly two objects, one with VarA set and one with VarB set? — sblom
– sblom, Commented Jan 26, 2012 at 8:19
Are you sure this is a good idea? It looks like you would be much better off by simply storing 1 object in the session, and write to one subset of the properties during "step1" and another subset during "step2". — Jonas Høgh
– Jonas Høgh, Commented Jan 26, 2012 at 8:38
@JonasH, MVC is de-serializing it, it means that I need to join them, I cannot tell mvc to de-serialize over an existing object. — SexyMF
– SexyMF, Commented Jan 26, 2012 at 8:41

toddmo · Accepted Answer · 2017-02-06 16:50:54Z

9

Here's the answer to the OP's question which is:

an exact answer
for two objects of the same type
- (for two objects of different types the code would be almost identical)
a solution that is not hard coded
using linq
that respects non-nullity of source values
that doesn't need an external library
in one line of code.

public static T Merge<T>(T target, T source)
{
  typeof(T)
  .GetProperties()
  .Select((PropertyInfo x) => new KeyValuePair<PropertyInfo, object>(x, x.GetValue(source, null)))
  .Where((KeyValuePair<PropertyInfo, object> x) => x.Value != null).ToList()
  .ForEach((KeyValuePair<PropertyInfo, object> x) => x.Key.SetValue(target, x.Value, null));

  //return the modified copy of Target
  return target;
}

edited Feb 6, 2017 at 16:50

answered Jul 2, 2014 at 18:47

toddmo

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1 Comment

toddmo Over a year ago

@A1rPun, I guess return target; is a line of code. So, one pretty line of code ಠ‿ಠ

Seb Boulet · Accepted Answer · 2012-01-26 09:33:32Z

3

Here's a way to accomplish this using reflection:

public class SomePropertyClass
{
    public string VarA { get; set; }
    public string VarB { get; set; }
}

static class Program
{
    static void Main(string[] args)
    {
        SomePropertyClass v1 = new SomePropertyClass() { VarA = "item 1" };
        SomePropertyClass v2 = new SomePropertyClass() { VarB = "item 2" };

        var yo = v1.Combine(v2);
    }

    static public IEnumerable<object> Combine<T, U>(this T one, U two)
    {
        var properties1 = one.GetType().GetProperties().Where(p => p.CanRead && p.GetValue(one, null) != null).Select(p => p.GetValue(one, null));
        var properties2 = two.GetType().GetProperties().Where(p => p.CanRead && p.GetValue(two, null) != null).Select(p => p.GetValue(two, null));

        return new List<object>(properties1.Concat(properties2));
    }
}

edited Jan 26, 2012 at 9:33

answered Jan 26, 2012 at 8:42

Seb Boulet

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1 Comment

Seb Boulet Over a year ago

Changed answer to use reflection in order to provided an auto mechanism.

Ian Mercer · Accepted Answer · 2012-01-26 08:40:43Z

3

Do you mean something like this ... a Merge method that takes whichever value is not null from the matching properties?

public class SomePropertyClass{
    public string VarA{get;set;}
    public string VarB{get;set;}

    public SomePropertyClass Merge (SomePropertyClass other)
    {
       return new SomePropertyClass 
                    { VarA = this.VarA ?? other.VarA, 
                      VarB = this.VarB ?? other.VarB 
                    };
    }

If you wanted a solution that would work for any class you'd need to use reflection to find all the properties and then copy the missing ones. }

answered Jan 26, 2012 at 8:40

Ian Mercer

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2 Comments

SexyMF Over a year ago

So there is no other cleaver auto-something that merge it? (-: ?

Ian Mercer Over a year ago

Not built in, you'll need to use reflection or some library like valueinjecter.codeplex.com

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