35 lines
1.3 KiB
Markdown
35 lines
1.3 KiB
Markdown
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---
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title: To Dictionary
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localeTitle: 到字典
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---
# ToDictionary
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从DataSet中创建一个Dictionary;
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### 签名
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```csharp
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Enumerable.ToDictionary<TSource, TKey> Method (IEnumerable<TSource>, Func<TSource, TKey>)
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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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// Generates a Dictionary of Fruits by Id
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var fruitsById = fruits.ToDictionary(k => k.Id, v => v); // Dictionary<int, Fruit>
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// Generates a dictionary fruits by color
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var fruitsByColor = fruits.GroupBy(g => g.Color).ToDictionary(k => k.Key, v => v.ToList()); // Dictionary of list of fruits by color
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// Generates a dictionary of quantity of fruits by color
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var fruitsByColor = fruits.GroupBy(g => g.Color).ToDictionary(k => k.Key, v => v.Sum(s => s.Quantity)); // Dictionary of sum of fruits by color
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```
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