Linq select top one related entity by date năm 2024

For example, you deserialize a JSON file into a list of Customer with the

var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 0 and a few other properties populated. Then you want to retrieve those customers from the database to update those properties.

A frequent solution is using the

var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 1 methods such as:

var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); It works great and is easy to use.

However, this solution has some limitations such as:

• It only supports basic types like var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 2 or var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 3
• The list of var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 4 is limited due to SQL limitations
• It doesn't support surrogate key (more than one key) or other complex scenarios

The WhereBulkContains method lets you filter a query by including all entities from the list. It's doesn't have any of the

var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 1 method limitations.

FAQ

How to use the method WhereBulkContains?

The most basic scenario is passing a list to the WhereBulkContains method.

The WhereBulkContains method will filter entities to include those contained in the list.

var customers = context.Customers.WhereBulkContains(deserializedCustomers); var customers = context.Customers.WhereBulkContains(deserializedCustomers, x => x.Code); var customers = context.Customers.WhereBulkContains(deserializedCustomers, new List { "Code" }); var customers = context.Customers.WhereBulkContains(deserializedCustomers, "Code"); Try it

The

var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 9 method is also supported.

What kind of list is supported?

All kinds of lists are supported. The only requirement is that your list is a basic type or contains a property with the same name as the key:

• Basic type such as var customers = context.Customers.WhereBulkContains(deserializedCustomers); var customers = context.Customers.WhereBulkContains(deserializedCustomers, x => x.Code); var customers = context.Customers.WhereBulkContains(deserializedCustomers, new List { "Code" }); var customers = context.Customers.WhereBulkContains(deserializedCustomers, "Code"); 0 and var customers = context.Customers.WhereBulkContains(deserializedCustomers); var customers = context.Customers.WhereBulkContains(deserializedCustomers, x => x.Code); var customers = context.Customers.WhereBulkContains(deserializedCustomers, new List { "Code" }); var customers = context.Customers.WhereBulkContains(deserializedCustomers, "Code"); 1
• Entity Type such as var customers = context.Customers.WhereBulkContains(deserializedCustomers); var customers = context.Customers.WhereBulkContains(deserializedCustomers, x => x.Code); var customers = context.Customers.WhereBulkContains(deserializedCustomers, new List { "Code" }); var customers = context.Customers.WhereBulkContains(deserializedCustomers, "Code"); 2
• Anonymous Type
• Expando Object list

{ var ids = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.WhereBulkContains(ids); } { var customers = context.Customers.WhereBulkContains(deserializedCustomers); } { var anonymousIds = deserializedCustomers.Select(x => new { x.CustomerID }).ToList(); var customers = context.Customers.WhereBulkContains(anonymousIds); } { var expandos = new List(); deserializedCustomers.ForEach(x => {

dynamic expando = new ExpandoObject();
expando.CustomerID = x.CustomerID;
expandos.Add(expando);

}); var customers = context.Customers.WhereBulkContains(expandos); } Try it

The

var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 9 method is also supported.

Can I use WhereBulkContains after a Where?

Yes, the WhereBulkContains is an extension method that you can chain like any other LINQ method. You can chain it before or after the

var customers = context.Customers.WhereBulkContains(deserializedCustomers); var customers = context.Customers.WhereBulkContains(deserializedCustomers, x => x.Code); var customers = context.Customers.WhereBulkContains(deserializedCustomers, new List { "Code" }); var customers = context.Customers.WhereBulkContains(deserializedCustomers, "Code"); 5 or any other LINQ methods.

var customers = context.Customers.Where(x => x.CustomerID >= 2).WhereBulkContains(deserializedCustomers); Try it

Can I use the WhereBulkContains with million of items?

Yes, you can use the WhereBulkContains method with an unlimited amount of items.

Under the hood, we create a temporary table and populated it with our very fast BulkInsert method. Then we use this temporary table to perform an

var customers = context.Customers.WhereBulkContains(deserializedCustomers); var customers = context.Customers.WhereBulkContains(deserializedCustomers, x => x.Code); var customers = context.Customers.WhereBulkContains(deserializedCustomers, new List { "Code" }); var customers = context.Customers.WhereBulkContains(deserializedCustomers, "Code"); 7 statement.

How can I use a custom key?

By default, we create the join using the entity key, but you can choose a custom key with one or many properties by passing:

• A lambda expression
• A list of string

var customers = context.Customers.WhereBulkContains(deserializedCustomers, x => x.Code); var customers = context.Customers.WhereBulkContains(deserializedCustomers, new List { "Code" }); var customers = context.Customers.WhereBulkContains(deserializedCustomers, "Code"); Try it

Can I use WhereBulkContains with Batch Operations?

The WhereBulkContains method is compatible with our batch methods:

• UpdateFromQuery
• DeleteFromQuery
• InsertFromQuery

context.Customers.WhereBulkContains(deserializedCustomers).UpdateFromQuery(x => new { FirstName = "UpdateFromQuery" }); context.Customers.WhereBulkNotContains(deserializedCustomers).DeleteFromQuery(); context.Customers.WhereBulkContains(deserializedCustomers).InsertFromQuery(x => new { x.Code, FirstName = "Copied", x.LastName, x.Email }); Try it

What are Contains method limitations?

Has said previously, the

var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 1 method already work great but also have his own limitations:

• It only supports basic types like var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 2 or var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 3
• The list of var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 4 is limited due to SQL limitations
• It doesn't support surrogate key (more than one key) or other complex scenarios

The WhereBulkContains doesn't have any of those limitations.

Do WhereBulkContains faster than Contains method?

In most scenarios, the answer will probably be no. The

var customerIds = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.Where(x => customerIds.Contains(x.CustomerID)).ToList(); 1 method is faster due to simply using a very basic

{ var ids = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.WhereBulkContains(ids); } { var customers = context.Customers.WhereBulkContains(deserializedCustomers); } { var anonymousIds = deserializedCustomers.Select(x => new { x.CustomerID }).ToList(); var customers = context.Customers.WhereBulkContains(anonymousIds); } { var expandos = new List(); deserializedCustomers.ForEach(x => {

dynamic expando = new ExpandoObject();
expando.CustomerID = x.CustomerID;
expandos.Add(expando);

}); var customers = context.Customers.WhereBulkContains(expandos); } 5 statement.

The WhereBulkContains method is also very fast, but the main advantage is his flexibility by supporting:

• An unlimited amount of items
• Any kind of list
• Custom key/surrogate key

What is the difference between the method WhereBulkContains, WhereBulkNotContains, and BulkRead?

The

{ var ids = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.WhereBulkContains(ids); } { var customers = context.Customers.WhereBulkContains(deserializedCustomers); } { var anonymousIds = deserializedCustomers.Select(x => new { x.CustomerID }).ToList(); var customers = context.Customers.WhereBulkContains(anonymousIds); } { var expandos = new List(); deserializedCustomers.ForEach(x => {

dynamic expando = new ExpandoObject();
expando.CustomerID = x.CustomerID;
expandos.Add(expando);

}); var customers = context.Customers.WhereBulkContains(expandos); } 7 method is similar to the WhereBulkContains method, but it filters entities not contained (

{ var ids = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.WhereBulkContains(ids); } { var customers = context.Customers.WhereBulkContains(deserializedCustomers); } { var anonymousIds = deserializedCustomers.Select(x => new { x.CustomerID }).ToList(); var customers = context.Customers.WhereBulkContains(anonymousIds); } { var expandos = new List(); deserializedCustomers.ForEach(x => {

dynamic expando = new ExpandoObject();
expando.CustomerID = x.CustomerID;
expandos.Add(expando);

}); var customers = context.Customers.WhereBulkContains(expandos); }

9. instead of contained (

var customers = context.Customers.Where(x => x.CustomerID >= 2).WhereBulkContains(deserializedCustomers); 0):

• The WhereBulkContains method filters entities to include entities from the list ( var customers = context.Customers.WhereBulkContains(deserializedCustomers); var customers = context.Customers.WhereBulkContains(deserializedCustomers, x => x.Code); var customers = context.Customers.WhereBulkContains(deserializedCustomers, new List { "Code" }); var customers = context.Customers.WhereBulkContains(deserializedCustomers, "Code"); 7 statement)
• The { var ids = deserializedCustomers.Select(x => x.CustomerID).ToList(); var customers = context.Customers.WhereBulkContains(ids); } { var customers = context.Customers.WhereBulkContains(deserializedCustomers); } { var anonymousIds = deserializedCustomers.Select(x => new { x.CustomerID }).ToList(); var customers = context.Customers.WhereBulkContains(anonymousIds); } { var expandos = new List(); deserializedCustomers.ForEach(x => {

  dynamic expando = new ExpandoObject();  
  expando.CustomerID = x.CustomerID;  
  expandos.Add(expando);  
  

  }); var customers = context.Customers.WhereBulkContains(expandos); } 7 method filters entities to exclude entities from the list ( var customers = context.Customers.Where(x => x.CustomerID >= 2).WhereBulkContains(deserializedCustomers); 4 statement).

As for the

var customers = context.Customers.Where(x => x.CustomerID >= 2).WhereBulkContains(deserializedCustomers); 5 method, under the hood calls the WhereBulkContains method followed by the

var customers = context.Customers.Where(x => x.CustomerID >= 2).WhereBulkContains(deserializedCustomers); 7 or

var customers = context.Customers.Where(x => x.CustomerID >= 2).WhereBulkContains(deserializedCustomers); 8 method.

How do I select top 5 records in LINQ?

Linq Query To Select Top 5 Records.

var list = (from t in ctn.Items..

where t.DeliverySelection == true && t.Delivery.SentForDelivery == null..

orderby t.Delivery.SubmissionDate..

select t). Take(5);.

What is the difference between first () and single () extension methods in LINQ?

Single() asserts that one and only one element exists in the sequence. First() simply gives you the first one. When to use? Use Single / SingleOrDefault() when you are sure there is only one record present in a database or you can say if you querying on a database with the help of the primary key of the table.

How to select certain elements in a list using LINQ methods?

In LINQ queries, the Where operator is used to select certain elements from a sequence. It expects an expression that evaluates to a boolean value. Every element satisfying the condition will be included in the resulting query.

How to add days to a date in LINQ query?

AddDays(Nullable, Nullable) When used as part of a LINQ to Entities query, this method invokes the canonical AddDays EDM function to add the given number of days to a date/time.