LINQ to SQL 集合運算：Concat、Union、Intersect、Except 四大運算子詳解

四大集合運算子比較

皆為延遲執行。

程式碼範例

Concat：合併電話與傳真

var q = (from c in db.Customers select c.Phone)
        .Concat(from c in db.Customers select c.Fax)
        .Concat(from e in db.Employees select e.HomePhone);

Concat 複合投影：客戶與員工姓名電話

var q = (from c in db.Customers select new { Name = c.CompanyName, c.Phone })
        .Concat(from e in db.Employees select new { Name = e.FirstName + " " + e.LastName, Phone = e.HomePhone });

Union：客戶與員工所在國家

var q = (from c in db.Customers select c.Country)
        .Union(from e in db.Employees select e.Country);

Intersect：客戶與員工共同國家

var q = (from c in db.Customers select c.Country)
        .Intersect(from e in db.Employees select e.Country);

Except：僅客戶所在國家（排除員工國家）

var q = (from c in db.Customers select c.Country)
        .Except(from e in db.Employees select e.Country);