使用字典

Question

按字母順序排列的字母（A - D，E - H，I - L等）存儲數據我正在使用實體框架，並且我想存儲特定範圍內的項目總數字母集（如果這是有道理的）：

A - D (12) - (where 12 is the total amount and the data falls between letters A and D). 
E - H (24) 
I - L (9) 
M - P (62) 
Q - T (18) 
U - Z (0) 

我不太確定如何使用Dictionary做到這一點。

假設我的模型對象由Id和Title組成，並且它被稱爲Discount。

目前，我有以下幾點：提前

List<Discount> discounts = new List<Discount>(); 
Dictionary<string, Discount> dict = new Dictionary<string, Discount>(); 
foreach (DiscountDTO discount in discounts) 
{ 
    if (discount.Title.StartsWith("A") || 
     discount.Title.StartsWith("B") || 
     discount.Title.StartsWith("C") || 
     discount.Title.StartsWith("D")) 
    { 
     dict.Add("A - D", discount); 
    } else if (discount.Title.StartsWith("E") || 
     discount.Title.StartsWith("F") || 
     discount.Title.StartsWith("G") || 
     discount.Title.StartsWith("H")) 
    { 
     dict.Add("E - H", discount); 
    } else if (discount.Title.StartsWith("I") || 
     discount.Title.StartsWith("J") || 
     discount.Title.StartsWith("K") || 
     discount.Title.StartsWith("L")) 
    { 
     dict.Add("I - L", discount); 
    } else if (discount.Title.StartsWith("M") || 
     discount.Title.StartsWith("N") || 
     discount.Title.StartsWith("O") || 
     discount.Title.StartsWith("P")) 
    { 
     dict.Add("M - P", discount); 
    } else if (discount.Title.StartsWith("Q") || 
     discount.Title.StartsWith("R") || 
     discount.Title.StartsWith("S") || 
     discount.Title.StartsWith("T")) 
    { 
     dict.Add("Q - T", discount); 
    } else if (discount.Title.StartsWith("U") || 
     discount.Title.StartsWith("V") || 
     discount.Title.StartsWith("W") || 
     discount.Title.StartsWith("X") || 
     discount.Title.StartsWith("Y") || 
     discount.Title.StartsWith("Z")) 
    { 
     dict.Add("U - Z", discount); 
    } 
} 

感謝。

Answer 1

你應該使用一個列表作爲字典的值：

static void Main(string[] args) 
{ 

    List<Discount> list = new List<Discount>(); 
    list.Add(new Discount { Id = 1, Title = "Adam" }); 
    list.Add(new Discount { Id = 2, Title = "Ben" }); 
    list.Add(new Discount { Id = 3, Title = "Alex" }); 
    list.Add(new Discount { Id = 4, Title = "Daniel" }); 
    list.Add(new Discount { Id = 5, Title = "Ethan" }); 
    list.Add(new Discount { Id = 6, Title = "Howard" }); 
    list.Add(new Discount { Id = 7, Title = "Peter" }); 
    list.Add(new Discount { Id = 8, Title = "Tazz" }); 
    list.Add(new Discount { Id = 9, Title = "Steve" }); 
    list.Add(new Discount { Id = 10, Title = "Lyle" }); 

    Dictionary<string, List<Discount>> dic = new Dictionary<string, List<Discount>>(); 
    foreach (Discount d in list) 
    { 
     string range = GetRange(d.Title); 
     if (dic.ContainsKey(range)) 
      dic[range].Add(d); 
     else 
      dic.Add(range, new List<Discount> { d }); 
    } 
} 

static string GetRange(string s) 
{ 
    char c = s.ToLower()[0]; 
    if (c >= 'a' && c <= 'd') 
     return "A - D"; 
    else if (c >= 'e' && c <= 'h') 
     return "E - H"; 
    else if (c >= 'i' && c <= 'l') 
     return "I - L"; 
    else if (c >= 'm' && c <= 'p') 
     return "M - P"; 
    else if (c >= 'q' && c <= 't') 
     return "Q - T"; 
    else if (c >= 'u' && c <= 'z') 
     return "U - Z"; 
    return ""; 
} 

Answer 2

這是你想要的東西：

static void Main(string[] args) 
    { 

    List<Discount> list = new List<Discount>(); 
    list.Add(new Discount { Id = 1, Title = "Adam" }); 
    list.Add(new Discount { Id = 2, Title = "Ben" }); 
    list.Add(new Discount { Id = 3, Title = "Alex" }); 
    list.Add(new Discount { Id = 4, Title = "Daniel" }); 
    list.Add(new Discount { Id = 5, Title = "Ethan" }); 
    list.Add(new Discount { Id = 6, Title = "Howard" }); 
    list.Add(new Discount { Id = 7, Title = "Peter" }); 
    list.Add(new Discount { Id = 8, Title = "Tazz" }); 
    list.Add(new Discount { Id = 9, Title = "Steve" }); 
    list.Add(new Discount { Id = 10, Title = "Lyle" }); 

    var query = list.GroupBy(d => GetRange(d.Title)); 

    foreach (var group in query) 
     Console.WriteLine("{0}[{1}]", group.Key, group.Count()); 
    } 

    static string GetRange(string s) 
    { 
     char c = s.ToLower()[0]; 
     if (c >= 'a' && c <= 'd') 
      return "A - D"; 
     else if (c >= 'e' && c <= 'h') 
      return "E - H"; 
     else if (c >= 'i' && c <= 'l') 
      return "I - L"; 
     else if (c >= 'm' && c <= 'p') 
      return "M - P"; 
     else if (c >= 'q' && c <= 't') 
      return "Q - T"; 
     else if (c >= 'u' && c <= 'z') 
      return "U - Z"; 
     return ""; 
    }