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LINQ query syntax always ends with a Select or Group clause. The Select clause is used to shape the data. You can select the whole object as it is or only some properties of it. In the above example, we selected the each resulted string elements.
Select is used to project individual element from List, in your case each customer from customerList . As Customer class contains property called Salary of type long, Select predicate will create new form of object which will contain only value of Salary property from Customer class.
Select() takes each source element, transforms it, and returns a sequence of the transformed values.
Select will always return the same number of elements in the list (regardless of a filter condition you may have). Where can return less elements depending on your filter condition.
The extensions methods also provide a ToDictionary extension. It is fairly simple to use, the general usage is passing a lambda selector for the key and getting the object as the value, but you can pass a lambda selector for both key and value.
class SomeObject
{
public int ID { get; set; }
public string Name { get; set; }
}
SomeObject[] objects = new SomeObject[]
{
new SomeObject { ID = 1, Name = "Hello" },
new SomeObject { ID = 2, Name = "World" }
};
Dictionary<int, string> objectDictionary = objects.ToDictionary(o => o.ID, o => o.Name);
Then objectDictionary[1] Would contain the value "Hello"
A more explicit option is to project collection to an IEnumerable of KeyValuePair and then convert it to a Dictionary.
Dictionary<int, string> dictionary = objects
.Select(x=> new KeyValuePair<int, string>(x.Id, x.Name))
.ToDictionary(x=>x.Key, x=>x.Value);
var dictionary = (from x in y
select new SomeClass
{
prop1 = value1,
prop2 = value2
}
).ToDictionary(item => item.prop1);
That's assuming that SomeClass.prop1 is the desired Key for the dictionary.
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