LINQ |过滤操作员|类型
原文:https://www . geesforgeks . org/linq-filling-operator-of type/
过滤运算符是那些用于根据给定数据源或给定序列的用户要求过滤数据的运算符。例如，在员工记录中，我们希望获得年龄在 21 岁的员工的数据。所以，我们根据他们的年龄过滤记录。在 LINQ，您可以使用以下运算符进行筛选:
- 其中
- 类型
类型运算符
OfType 运算符根据序列或数据源将集合中的元素强制转换为指定类型的能力来筛选序列或数据源。它是通过使用延迟执行来实现的，这意味着它会立即返回一个包含执行操作所需信息的对象，但是当该对象通过使用 foreach 循环或 for 循环在循环上迭代时，它就会执行。
- 在 LINQ，您可以在一个查询中使用多个类型。
-
It does not support query syntax in C# or VB.Net language, but you can use it with syntax as shown in the below example.
示例:
```cs // C# program to illustrate the // concept of OfType operator using System; using System.Linq; using System.Collections;
// Employee details public class Employee {
public int emp_id { get; set; } public string emp_name { get; set; } public string emp_gender { get; set; } public string emp_hire_date { get; set; } public int emp_salary { get; set; } }
public class GFG {
// Main method static public void Main() {
// Data Source ArrayList myarray = new ArrayList(); myarray.Add("GeeksforGeeks"); myarray.Add(23); myarray.Add(new Employee() {emp_id = 209, emp_name = "Anjita"}); myarray.Add(new Employee() {emp_id = 210, emp_name = "Soniya"}); myarray.Add(new Employee() {emp_id = 300, emp_name = "Rohan"});
// Using OfType operator var res1 = from e1 in myarray.OfType() select e1;
foreach(var val1 in res1) { Console.WriteLine(val1); }
var res2 = from e2 in myarray.OfType() select e2;
foreach(var val2 in res2) { Console.WriteLine(val2.emp_name); } } } ```
Output:
```cs GeeksforGeeks Anjita Soniya Rohan
```
-
It supports method syntax in C# or in VB. It available in both the Queryable and Enumerable class. As shown in the below example.
示例:
```cs // C# program to illustrate the // concept of OfType operator using System; using System.Linq; using System.Collections;
// Employee details public class Employee {
public int emp_id { get; set; } public string emp_name { get; set; } public string emp_gender { get; set; } public string emp_hire_date { get; set; } public int emp_salary { get; set; } }
class GFG {
// Main method static public void Main() {
// Data Source ArrayList myarray = new ArrayList(); myarray.Add(new Employee() {emp_id = 209, emp_name = "Anjita"}); myarray.Add(new Employee() {emp_id = 210, emp_name = "Soniya"}); myarray.Add(new Employee() {emp_id = 300, emp_name = "Rohan"});
// Get the id of the employees // Using OfType operator var res = myarray.OfType();
foreach(var val in res) { Console.WriteLine("Employee Id: {0}", val.emp_id); } } } ```
Output:
```cs Employee Id: 209 Employee Id: 210 Employee Id: 300
```
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