31 lines
1.1 KiB
Markdown
31 lines
1.1 KiB
Markdown
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---
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title: Single Or Default
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localeTitle: 单一或默认
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---
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# 的SingleOrDefault
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返回满足指定条件的序列中的单个元素，如果未找到任何元素，则返回默认值。如果找到满足指定条件的多个元素，则该方法将抛出异常。
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### 签名
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```csharp
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Enumerable.SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>)
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```
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## 例
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```csharp
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var fruits = new List<Fruit>() {
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new Fruit() { Id = 1, Name = "Orange", Color = "Orange", Quantity: 3 },
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new Fruit() { Id = 2, Name = "Strawberry", Color = "Red", Quantity: 12 },
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new Fruit() { Id = 3, Name = "Grape", Color = "Purple", Quantity: 25 },
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new Fruit() { Id = 4, Name = "Pineapple", Color = "Yellow", Quantity: 1 },
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new Fruit() { Id = 5, Name = "Apple", Color = "Red", Quantity: 5 },
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new Fruit() { Id = 6, Name = "Mango", Color = "Yellow", Quantity: 2 }
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};
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var purpleFruit = fruits.SingleOrDefault(f => f.Color == "Purple"); // Grape
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var greenFruit = fruits.SingleOrDefault(f => f.Color == "Green"); // null
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```
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