How to update an object in a List<> in C#

How to update an object in a List<> in C#

I have a List<> of custom objects.
I need to find an object in this list by some property which is unique and update another property of this object. 
What is the quickest way to do it?


Answer 1:

Using Linq to find the object you can do:

var obj = myList.FirstOrDefault(x => x.MyProperty == myValue);
if (obj != null) obj.OtherProperty = newValue;

But in this case you might want to save the List into a Dictionary and use this instead:

// ... define after getting the List/Enumerable/whatever
var dict = myList.ToDictionary(x => x.MyProperty);
// ... somewhere in code
MyObject found;
if (dict.TryGetValue(myValue, out found)) found.OtherProperty = newValue;

Answer 2:

Just to add to CKoenig’s response. His answer will work as long as the class you’re dealing with is a reference type (like a class). If the custom object were a struct, this is a value type, and the results of .FirstOrDefault will give you a local copy of that, which will mean it won’t persist back to the collection, as this example shows:

struct MyStruct
    public int TheValue { get; set; }

Test code:

List<MyStruct> coll = new List<MyStruct> {
                                            new MyStruct {TheValue = 10},
                                            new MyStruct {TheValue = 1},
                                            new MyStruct {TheValue = 145},
var found = coll.FirstOrDefault(c => c.TheValue == 1);
found.TheValue = 12;

foreach (var myStruct in coll)

The output is 10,1,145

Change the struct to a class and the output is 10,12,145


Answer 3:

or without linq

foreach(MyObject obj in myList)
   if(obj.prop == someValue)
     obj.otherProp = newValue;

Answer 4:

Can also try.

 _lstProductDetail.Where(S => S.ProductID == "")
        .Select(S => { S.ProductPcs = "Update Value" ; return S; }).ToList();

Answer 5:

var itemIndex = listObject.FindIndex(x => x == SomeSpecialCondition());
var item = listObject.ElementAt(itemIndex);
item.SomePropYouWantToChange = "yourNewValue";

Answer 6:

You can do somthing like :

if (product != null) {
    var products = Repository.Products;
    var indexOf = products.IndexOf(products.Find(p => p.Id == product.Id));
    Repository.Products[indexOf] = product;
    // or 
    Repository.Products[indexOf].prop = product.prop;

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