30 lines
1003 B
Markdown
30 lines
1003 B
Markdown
---
|
|
title: First Or Default
|
|
localeTitle: 第一或默认
|
|
---
|
|
# FirstOrDefault
|
|
|
|
返回满足可选给定条件的第一个元素。如果未找到任何元素,则返回该对象的`default()`
|
|
|
|
### 签名
|
|
|
|
```csharp
|
|
Enumerable.FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>)
|
|
```
|
|
|
|
## 例
|
|
|
|
```csharp
|
|
var fruits = new List<Fruit>() {
|
|
new Fruit() { Id = 1, Name = "Orange", Color = "Orange", Quantity: 3 },
|
|
new Fruit() { Id = 2, Name = "Strawberry", Color = "Red", Quantity: 12 },
|
|
new Fruit() { Id = 3, Name = "Grape", Color = "Purple", Quantity: 25 },
|
|
new Fruit() { Id = 4, Name = "Pineapple", Color = "Yellow", Quantity: 1 },
|
|
new Fruit() { Id = 5, Name = "Apple", Color = "Red", Quantity: 5 },
|
|
new Fruit() { Id = 6, Name = "Mango", Color = "Yellow", Quantity: 2 }
|
|
};
|
|
|
|
var firstFruit = fruits.FirstOrDefault(); // Orange
|
|
|
|
var firstYellowFruit = fruits.FirstOrDefault(f => f.Color == "Green"); // null
|
|
|
|
``` |