Remove objects exsiting in another list in C#

To remove list items that exist in another list, you can use LINQ to create a new list that only contains items that do not exist in the other list. Here's an example:

List<int> numbers1 = new List<int>() { 1, 2, 3, 4, 5 };
List<int> numbers2 = new List<int>() { 3, 4, 5, 6, 7 };
List<int> result = numbers1.Except(numbers2).ToList();

In this example, we have two lists of integers, numbers1 and numbers2. We use the Except method to create a new list that contains only the items in numbers1 that do not exist in numbers2. We then convert the result to a new list using the ToList method.

To remove list items by a property that exists in another list, you can use LINQ to create a new list that only contains items that do not have a matching property value in the other list. Here's an example:

class MyClass
{
    public int Id { get; set; }
    public string Name { get; set; }
}

List<MyClass> list1 = new List<MyClass>()
{
    new MyClass() { Id = 1, Name = "John" },
    new MyClass() { Id = 2, Name = "Mary" },
    new MyClass() { Id = 3, Name = "Bob" },
    new MyClass() { Id = 4, Name = "Alice" },
};

List<MyClass> list2 = new List<MyClass>()
{
    new MyClass() { Id = 1, Name = "John" },
    new MyClass() { Id = 3, Name = "Bob" },
};

List<MyClass> result = list1.Where(x => !list2.Any(y => y.Id == x.Id)).ToList();

In this example, we have two lists of MyClass objects, list1 and list2. We use LINQ to create a new list that contains only the items in list1 that do not have a matching Id property value in list2. We do this by using the Where method to filter the items in list1, and the Any method to check if there are any items in list2 that have a matching Id property value. We then convert the result to a new list using the ToList method.

Removing common elements from two lists in C#:

List<T> uniqueList = list1.Except(list2).ToList();

Remove items from list if they exist in another list in C#:
```
list1.RemoveAll(item => list2.Contains(item));
```

C# LINQ remove items from one list based on another list:

List<T> uniqueList = list1.Where(item => !list2.Contains(item)).ToList();

Remove common objects between two lists in C#:

List<T> uniqueList = list1.Except(list2).ToList();

C# remove objects from list using Except:

List<T> uniqueList = list1.Except(list2).ToList();

Exclude elements from one list that are in another list in C#:
```
List<T> uniqueList = list1.Except(list2).ToList();
```

C# remove objects from list based on another list condition:

list1.RemoveAll(item => list2.Any(otherItem => /* condition to match items */));

Remove items from List<T> using Intersect in C#:

List<T> uniqueList = list1.Intersect(list2).ToList();

C# remove objects from list using Where and Any:

list1 = list1.Where(item => !list2.Any(otherItem => /* condition to match items */)).ToList();

Remove elements from List<T> if they exist in another list in C#:
```
list1.RemoveAll(item => list2.Contains(item));
```

C# remove objects from list using Except with custom equality comparison:

List<T> uniqueList = list1.Except(list2, new CustomEqualityComparer()).ToList();

Remove items from ObservableCollection based on another ObservableCollection in C#:
```
foreach (var item in collection2)
{
    collection1.Remove(item);
}
```

C# remove objects from list using LINQ and Contains:

list1 = list1.Where(item => !list2.Contains(item)).ToList();

Remove objects from HashSet if they exist in another HashSet in C#:
```
hashSet1.ExceptWith(hashSet2);
```
C# remove objects from list based on another list using RemoveAll:
```
list1.RemoveAll(item => list2.Contains(item));
```

Remove common elements from two arrays in C#:

T[] uniqueArray = array1.Except(array2).ToArray();

C# remove items from list based on another list property:

list1.RemoveAll(item => list2.Any(otherItem => otherItem.PropertyToCheck == item.PropertyToCheck));

Remove objects from ConcurrentDictionary if they exist in another ConcurrentDictionary in C#:
```
foreach (var key in dictionary2.Keys)
{
    dictionary1.TryRemove(key, out _);
}
```

C# remove objects from list using Intersect with custom equality comparison:

List<T> uniqueList = list1.Intersect(list2, new CustomEqualityComparer()).ToList();