如何以編程方式查詢DbContext中的DbSet？

Question

我想建立一個控制器，爲我所有的查找表編輯請求。我有我的DbContext從IdNamePairBase派生，e.g幾個DbSet變量：

public DbSet<Country> Countries { get; set; } // Country derives from IdNamePairBase 

如何傳遞的其中之一的名稱查詢，以獲得在該列表中的所有項目？例如。

var list = db.GetNamedDbSet("Countries"); 

然後，加分，我需要從list得到一個IEnumerable<IdNamePairBase>。

Answer 1

如果表的名稱與類型相對應，則可以在DbContext上使用Set(Type type)。

public IEnumerable<IdNamePairBase> GetNamedDbSet(string dbSetName) 
{ 
     var property = Type.GetType(dbSetName); 
     if (property == null || !property.CanRead) 
     { 
     throw new ArgumentException("DbSet named " + dbSetName + " does not exist."); 
     } 

     // at this point you might want to check that the property is an enumerable type 
     // and that the generic definition is convertible to IdNamePairBase by 
     // inspecting the property type. If you're sure that these hold, you could 
     // omit the check. 

     return Set(type).Cast<IdNamePairBase>(); 
} 

原來的答案

如果集的名稱相匹配的屬性名稱，你可以使用反射。

public IEnumerable<IdNamePairBase> GetNamedDbSet(string dbSetName) 
{ 
     var property = this.GetType().GetProperty(dbSetName); 
     if (property == null || !property.CanRead) 
     { 
     throw new ArgumentException("DbSet named " + dbSetName + " does not exist."); 
     } 

     // at this point you might want to check that the property is an enumerable type 
     // and that the generic definition is convertible to IdNamePairBase by 
     // inspecting the property type. If you're sure that these hold, you could 
     // omit the check. 

     var result = new List<IdNamePairBase>(); 
     foreach (var item in (IEnumerable)property.GetValue(this, null)) 
     { 
      result.Add((IdNamePairBase)item); 
     } 
     return result; 
}