C＃：獲取屬性的名稱，並檢查它的價值

Question

我有下面的類專營：

public class Franchise 
     { 
      public string FolderName { get; set; } 
      public string InstallerExeName { get; set; } 
     } 

我有檢查在數據庫中的所有特權中uniqness特定的屬性值的方法。

public bool ValidateFolderName(string folderName) 
     { 
      var allFranchises = _franchiseService.GetAll(); 
      var result = allFranchises.Any(f => f.FolderName == folderName); 
      return result; 
     } 

的問題是我要檢查他人財產爲uniqness：

public bool ValidateInstallerExeName(string installerExeName) 
     { 
      var allFranchises = _franchiseService.GetAll(); 
      var result = allFranchises.Any(f => f.InstallerExeName == installerExeName); 
      return result; 
     } 

我想通過一個通用的方法，以避免重複代碼。喜歡的東西：

public bool ValidateProperty(string propertyName) 
     { 
      var allFranchises = _franchiseService.GetAll(); 
      // Not sure how to write this line 
      var result = allFranchises.Any(f => f.[propertyName] == propertyName); 
      return result; 
     } 

的問題是我不知道如何重新寫這行代碼，以便它可以獲取屬性名稱和所提供的參數檢查其值：

var result = allFranchises.Any(f => f.[propertyName] == propertyName); 

我知道我可以做這樣的事情與反思：

franchise.GetType().GetProperty(propertyName).GetValue(franchise, null);

，但我不知道我怎樣才能使這個適合我的情況。任何工作示例的幫助將不勝感激。謝謝！

Answer 1

下面是使用反射一個完整的工作示例：

class Program 
{ 
    private static List<Franchise> allFranchises; 

    static void Main(string[] args) 
    { 
     allFranchises = new List<Franchise> 
     { 
      new Franchise() { FolderName=@"c:\1", InstallerExeName="1.exe" }, 
      new Franchise() { FolderName=@"c:\2", InstallerExeName="2.exe" }, 
      new Franchise() { FolderName=@"c:\3", InstallerExeName="3.exe" }, 
      new Franchise() { FolderName=@"c:\4", InstallerExeName="4.exe" }, 
      new Franchise() { FolderName=@"c:\5", InstallerExeName="5.exe" }, 
     }; 

     Console.WriteLine(ValidateProperty("FolderName", @"c:\2", allFranchises)); 
     Console.WriteLine(ValidateProperty("InstallerExeName", "5.exe", allFranchises)); 
     Console.WriteLine(ValidateProperty("FolderName", @"c:\7", allFranchises)); 
     Console.WriteLine(ValidateProperty("InstallerExeName", "12.exe", allFranchises)); 
    } 

    public static bool ValidateProperty(string propertyName, object propertyValue, IEnumerable<Franchise> validateAgainst) 
    { 
     PropertyInfo propertyInfo = typeof(Franchise).GetProperty(propertyName); 
     return validateAgainst.Any(f => propertyInfo.GetValue(f, null) == propertyValue); 
    } 
} 

public class Franchise 
{ 
    public string FolderName { get; set; } 
    public string InstallerExeName { get; set; } 
} 

它會打印出：

True 
True 
False 
False 

預期。

Answer 2

你可以使用擴展方法：

public static bool ValidateProperty(
    this IEnumerable<Franchise> franchises, 
    string property, 
    object value) 
{ 
    var prop = typeof(Franchise).GetProperty(property); 
    if (prop == null) 
     throw new ArgumentException("Property does not exist"); 
    return franchises.Any(f => 
     prop.GetValue(f) == value); 
} 

使用方法如下：

var r = _franchiseService.GetAll().ValidateProperty("FolderName", "myfolder1"); 

Answer 3

public bool ValidateProperty<TType, TPropertyType>(Func<TType, TPropertyType> propertySelector, TPropertyType propertyValue) 
{ 
    return _franchiseService.GetAll().Any(f => propertySelector(f) == propertyValue); 
} 

你可以這樣調用：

if(ValidateProperty(x => x.FirstName, "Joe")) 

這不使用反射，你有智能感知你的財產名稱也是如此。

Answer 4

您可以生成你想要使用System.Linq.Expressions

public class Franchise 
{ 
    public string FolderName { get; set; } 
    public string InstallerExeName { get; set; } 

    bool ValidateProperty(string propertyName) { 
    var allFranchises = new List<Franchise>(); 
    var parameter = Expression.Parameter(typeof(Franchise)); 
    var property = Expression.Property(parameter, propertyName); 
    var thisExpression = Expression.Constant(this, typeof(Franchise)); 
    var value = Expression.Property(thisExpression, propertyName); 
    var notThis = Expression.ReferenceNotEqual(thisExpression, property); 
    var equal = Expression.Equal(value, property); 
    var lambda = Expression.Lambda<Func<Franchise, bool>>(Expression.And(notThis, equal)); 


    // lamda is now the equivalent of: 
    // x => !object.ReferenceEquals(this, x) && object.Equals(x.Property, this.Property)  
    return allFranchises.Any(lambda.Compile()); 
    } 
} 

功能如果allFranchises的類型爲IQueryable的使用allFranchises.Any(lambda)

你也可以緩存，如果你擔心性能，供以後使用的表達。 }