Getting differences from objects with generics

Question

I'm trying to improve myself with generics but actually I dont know how to even start this task:

I need to build a method that will record two tables with logs. This method will recieve two objects of the same type and then I need them to be compared.

That the first table will be recorded with the name of the object.

The second table will receive the following data: the first table record ID, field name, old value and new value.

I need this to be build with generics since I have MANY different objects and I'm sure that's going to be painful and weird to build any kind of switch case for each object that I want to record those information.

I hope you guys help me !

SventoryMang · Accepted Answer · 2012-01-27 21:43:16Z

1

Unless these objects share a common interface you'll have to use reflection to get the properties of an object, then loop through them and compare the values between objectA and objectB. Something like this:

public void CompareTwoObjectsAndSaveChanges<TObjectType>(TObjectType objectA, TObjectType objectB )
    {
        //makes sure both objects match in Type
        if(objectA.GetType() == objectB.GetType())
        {
           //uses reflection to get all the properties of that object.
           foreach (var prop in objectA.GetType().GetProperties())
           {
               //checks to see if the value is different
               if(prop.GetValue(objectA, null) != prop.GetValue(objectB, null))
               {
                   //get the property name and its two different values
                   string nameOfPropertyThatChanges = prop.Name;
                   string objectAValue = prop.GetValue(objectA, null).ToString();
                   string objectBValue = prop.GetValue(objectB, null).ToString();

                   //logic to save to database
               }
           }   
        }
    }

You'll have to have oldValue and newValue columns be set to varchar or nvarchar in the database and convert all property values to strings before saving, otherwise you can't do what you are asking. Technically you wouldn't even have to use generics here as both parameters could simply take an object and the reflection would still work AS LONG AS both objects were the same type. The generic parameter here just makes it a bit more clean and makes sure that the person calling this method can't pass in two objects of different types accidently.

EDIT: To get the name of the object for your first table you would do:

typeof(TObjectType).ToString();

edited Jan 27, 2012 at 21:43

answered Jan 27, 2012 at 20:16

SventoryMang

10.5k15 gold badges74 silver badges118 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Brian Rudolph Over a year ago

Except really he should be verifying that objectA.GetType() == objectB.GetType() and be using objectA.GetType().GetProperties(), that way you are checking the data on all of the runtime data rather than just compile-time. Because if at compile-time the objects are casted down to (System.Object), it won't be checking any relevant properties at all.

Collectives™ on Stack Overflow

Getting differences from objects with generics

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related