lundi 8 juillet 2019

How use Reflection to condition multiple properties to check for equality in a LINQ .Where statement, depending on what class is passed?

I'm trying to generalize a duplicate checker function, which depending on which type of object, checks the properties said class has (provided in a configuration) are equal to those in another list.

I have decided to create a Dictionary, which will accept a type string for the key (Book, Author, Shop, etc.) and an array of properties that need to be equal.

Example of Dictionary enties:

"Book", ["Title", "CoverImage", "NumberOfPages"] 
"Author", ["Name", "Address", "SomethingElse"]

Then, I pass an object to the function and use Reflection to get the name of the type...

obj.GetType().Name;

... which I then use to fetch the right KVP from the Dictionary, meaning that if I pass a Book object, I get "Book". We then use that to get the configuration via ...

configDictionary["obj.GetType().Name"]

... which gives us the array of strings that are the properties that we need to check equality on.

I've gotten to the part where I need something along the lines of

list.Where(x => --> for each of the strings in the array - x.GetType.GetProperty(string) && --> same for next string && same for next string

... and then I need to top it off with an...

x.Id != obj.Id

To make sure we check for duplicates based on our logic (different id's and matches on all properties but has different Id's thus - a duplicate).

The end query should look like

Books:

someList.Where(x => 
x.Title == obj.Title 
&& x.CoverImage == obj.CoverImage 
&& x.NumberOfPages == obj.NumberOfPages 
&& x.Id != obj.Id)
.FirstOrDefault();

Authors:

someList.Where(x => x.Name == obj.Name 
&& x.Address == obj.Address 
&& x.SomethingElse == obj.SomethingElse 
&& x.Id != obj.Id)FirstOrDefault();





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