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[英]C#: Gets unmatched elements between 2 collections with Linq & Lambda
[英]How to make C# Linq Join to get unmatched elements in List
這是我的代碼示例。
var prmsMySql = new List<MySqlParameter>();
var prms = new List<SqlParameter>();
foreach (var objSql in prms)
{
flag = false;
foreach (var mySql in prmsMySql)
{
if (Convert.ToString(objSql.Value) == Convert.ToString(mySql.Value))
{
flag = true;
break;
}
}
if (!flag)
{
break;
}
}
我需要查找兩個列表是否具有相同的值,我的意思是prmsMySql值和prms值(Sqlparameter和MySqlparameter中的Value字段)。
此代碼可以正常工作。 是否有可能使linq實現以使代碼更短且更易於閱讀。
我嘗試了以下查詢。
var flag2 = prms.SelectMany(o => prmsMySql.Where(p => Convert.ToString(o.Value) !=
Convert.ToString(p.Value)).Distinct());
它給出了錯誤的答案。 請幫助我。 提前致謝 !!
這樣的事情應該起作用:
prmsMySql.Any(x => prms.Any(p => p.Value.ToString() == x.Value.ToString());
或join
(from p1 in prmsMySql
join p2 in prms
on p1.Value.ToString() equals p2.Value.ToString()
select p1).Any()
class MySqlParameter
{
public string Value { get; set; }
}
...
var lst1 = new List<MySqlParameter> {new MySqlParameter {Value="1"},
new MySqlParameter {Value="2"},
new MySqlParameter {Value="3"},
new MySqlParameter {Value="4"}};
var lst2 = new List<MySqlParameter> {new MySqlParameter {Value="1"},
new MySqlParameter {Value="2"},
new MySqlParameter {Value="3"},
new MySqlParameter {Value="7"}};
var res = from l1 in lst1
join l2 in lst2
on l1.Value equals l2.Value
select new { result = l1 };
bool flag = res.Count()==lst1.Count();
這是您內部foreach循環的LINQ代碼
foreach (var objSql in prms)
{
flag = prmsMySql.Any(mySql => Convert.ToString(objSql.Value) == Convert.ToString(mySql.Value));
if (flag)
continue;
break;
}
您是否要執行左外部聯接?
如何:執行左外部聯接(C#編程指南)
左外部聯接是一個聯接,在該聯接中將返回第一個集合的每個元素,而不管它在第二個集合中是否具有任何相關元素。 通過對組聯接的結果調用DefaultIfEmpty方法,可以使用LINQ執行左外部聯接。
class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
class Pet
{
public string Name { get; set; }
public Person Owner { get; set; }
}
public static void LeftOuterJoinExample()
{
Person magnus = new Person { FirstName = "Magnus", LastName = "Hedlund" };
Person terry = new Person { FirstName = "Terry", LastName = "Adams" };
Person charlotte = new Person { FirstName = "Charlotte", LastName = "Weiss" };
Person arlene = new Person { FirstName = "Arlene", LastName = "Huff" };
Pet barley = new Pet { Name = "Barley", Owner = terry };
Pet boots = new Pet { Name = "Boots", Owner = terry };
Pet whiskers = new Pet { Name = "Whiskers", Owner = charlotte };
Pet bluemoon = new Pet { Name = "Blue Moon", Owner = terry };
Pet daisy = new Pet { Name = "Daisy", Owner = magnus };
// Create two lists.
List<Person> people = new List<Person> { magnus, terry, charlotte, arlene };
List<Pet> pets = new List<Pet> { barley, boots, whiskers, bluemoon, daisy };
var query = from person in people
join pet in pets on person equals pet.Owner into gj
from subpet in gj.DefaultIfEmpty()
select new { person.FirstName, PetName = (subpet == null ? String.Empty : subpet.Name) };
foreach (var v in query)
{
Console.WriteLine("{0,-15}{1}", v.FirstName + ":", v.PetName);
}
}
// This code produces the following output:
//
// Magnus: Daisy
// Terry: Barley
// Terry: Boots
// Terry: Blue Moon
// Charlotte: Whiskers
// Arlene:
修改此代碼以對您的類進行操作;
如果滿足以下條件,則內容相同:
Count
與您的prms
設置相同 聯接是導入的數據庫工具。 那么在可能的情況下利用它對您有利。
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