我有一個 linq 查詢，它回傳幾個環大小的計數。但是，即使它在一定程度上可以重復使用，我也想看看我是否可以改進它。
private async Task<RingSizeLettersDto> CountOfLettersByRingFingerAsync(Func<RingSize, string> selector)
{
var ringSizes = await _ringSizeRepository.Get();
RingSizeLettersDto ringSizeLetters = new RingSizeLettersDto();
ringSizeLetters.G = ringSizes.Where(x => selector(x) == "G").Count();
ringSizeLetters.H = ringSizes.Where(x => selector(x) == "H").Count();
ringSizeLetters.I = ringSizes.Where(x => selector(x) == "I").Count();
ringSizeLetters.J = ringSizes.Where(x => selector(x) == "J").Count();
ringSizeLetters.K = ringSizes.Where(x => selector(x) == "K").Count();
ringSizeLetters.L = ringSizes.Where(x => selector(x) == "L").Count();
ringSizeLetters.M = ringSizes.Where(x => selector(x) == "M").Count();
ringSizeLetters.N = ringSizes.Where(x => selector(x) == "N").Count();
ringSizeLetters.O = ringSizes.Where(x => selector(x) == "O").Count();
ringSizeLetters.P = ringSizes.Where(x => selector(x) == "P").Count();
ringSizeLetters.Q = ringSizes.Where(x => selector(x) == "Q").Count();
ringSizeLetters.R = ringSizes.Where(x => selector(x) == "R").Count();
ringSizeLetters.S = ringSizes.Where(x => selector(x) == "S").Count();
ringSizeLetters.T = ringSizes.Where(x => selector(x) == "T").Count();
ringSizeLetters.U = ringSizes.Where(x => selector(x) == "U").Count();
ringSizeLetters.V = ringSizes.Where(x => selector(x) == "V").Count();
ringSizeLetters.W = ringSizes.Where(x => selector(x) == "W").Count();
ringSizeLetters.X = ringSizes.Where(x => selector(x) == "X").Count();
ringSizeLetters.Y = ringSizes.Where(x => selector(x) == "Y").Count();
ringSizeLetters.Z = ringSizes.Where(x => selector(x) == "Z").Count();
ringSizeLetters.Z1 = ringSizes.Where(x => selector(x) == "Z1").Count();
ringSizeLetters.Z2 = ringSizes.Where(x => selector(x) == "Z2").Count();
ringSizeLetters.Z3 = ringSizes.Where(x => selector(x) == "Z3").Count();
ringSizeLetters.Z4 = ringSizes.Where(x => selector(x) == "Z4").Count();
ringSizeLetters.Z5 = ringSizes.Where(x => selector(x) == "Z5").Count();
ringSizeLetters.Z6 = ringSizes.Where(x => selector(x) == "Z6").Count();
ringSizeLetters.NA = ringSizes.Where(x => selector(x) == "N/A").Count();
return ringSizeLetters;
}
uj5u.com熱心網友回復：
我有兩個改進：
您可以使用
Count(x => selector(x) == "G")，這將減少每行 1 個方法呼叫。您可以創建一個
Dictionary<string, int>（可能char因為鍵可以更準確）表示按字符計數，然后在應用程式的其他地方您可以使用要搜索的字符作為鍵來訪問它：
var ringSizes = new[] { 1, 2, 2 };
var ringSizeLetters = ringSizes.GroupBy(x => Selector(x))
.ToDictionary(x => x.Key, v => v.Count());
var ocurrences = ringSizeLetters["A"];
uj5u.com熱心網友回復：
如果您真的想要它們，您可以保留所有屬性：
class RingSizeDto{
public int G { get; set;}
public int H { get; set;}
...并通過使用例如字典來支持它們來避免反射：
class RingSizeDto{
private Dictionary<string, int> _ringSizes = new();
public int G { get => _ringSizes[nameof(G)]; set _ringSizes[nameof(G)] = value; }
public int H { get => _ringSizes[nameof(H)]; set _ringSizes[nameof(H)] = value; }
...
這意味著可以通過提供字典一次性設定大小：
public RingSizeDto(Dictionary <string, int> sizes){
_ringSizes = sizes;
}
字典可以通過查詢生成，例如
var sizes = someSizeList.GroupBy(s => s.SizeLetter).ToDictionary(g => g.Key, g => g.Count());
new RingSizeDto(sizes);
筆記; 如果您的串列沒有所有可能的大小，您將希望通過使用 TryGetValue 來避免字典訪問崩潰
public int G { get => _ringSizes.TryGetValue(nameof(G), out var x) ? x : 0; set _ringSizes[nameof(G)] = value; }
uj5u.com熱心網友回復：
根據您的特定用例是否允許這樣做，更簡潔的解決方案是使用字典。從你的代碼來看，最好的型別是IDictionary<string, int>. 其中，字串鍵是識別符號（例如'Z1'），整數值是 的結果.Count()。
我在下面列出了一個可能的代碼示例；
public static IDictionary<string, int> GetRingSizeLettersAsDict(
IEnumerable<string> sizeLetters,
IEnumerable<object> ringSizes)
{
IDictionary<string, int> ringSizeLetters = new();
sizeLetters.Select(
sl => ringSizeLetters.Add(
sl,
ringSizes.Where(rs => selector(rs).Equals(sl)).Count())
);
return ringSizeLetters;
}
這只是眾多解決方案之一，但它應該與您的代碼示例相同，前提是它適合您的用例。
uj5u.com熱心網友回復：
這是一種偽代碼，但像這樣的東西應該可以解決問題..
它是通過 System.Reflection 完成的
PropertyInfo[] properties = ringSizeLetters.GetProperties();
foreach (PropertyInfo property in properties)
{
var propertyName = property.Name;
var ringsizeValue = ringSizes.SingleOrDefault(x=> x.PROPERTYNAME == propertyName)
// if it finds ringsize Value
if(ringsizeValue != null)
{
property.SetValue(ringSizeLetters, ringsizeValue.Count());
}
}
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