C# 如何将 var 转换为 DataTable？
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How to Convert var to DataTable?
提问by RTRokzzz
I have following function -
我有以下功能 -
public static DataTable getDetails(PersonContext context)
{
DataTable dt = new DataTable();
IQueryable<Person> query = from p in context.Persons.Include("Employee")
.Include("Manager")
.Include("Activity")
where p.Activity.IsActive
select p;
var sorted = query.ToArray().OrderByDescending(p=>p.Activity.DateCreated);
dt = (DataTable)sorted;
return dt;
}
I can't test it. My question is - will this function work. If no what changes should I make in it?
我无法测试它。我的问题是 - 这个功能会起作用吗？如果没有，我应该对其进行哪些更改？
Update
更新
public static DataTable getDetails(PersonContext context)
{
DataTable dt = new DataTable("Details");
dt.Columns.Add("Name");
dt.Columns.Add("Department");
dt.Columns.Add("IsManager");
IQueryable<Person> query = from p in context.Persons.Include("Employee")
.Include("Manager")
.Include("Activity")
where p.Activity.IsActive
select p;
var sorted = query.ToArray().OrderByDescending(p=>p.Activity.DateCreated);
foreach(Person p in sorted)
{
dt.Rows.Add(p.Name, p.Employee.Department,p.Manager.IsManager);
}
return dt;
}
采纳答案by prthrokz
dt = (DataTable)sorted;
is an invalid cast. The correct way is to add the returned array to dt using dt.Rows.Add(query.ToArray().OrderByDescending(p=>p.Activity.DateCreated).toArray());.
You can find more information at Adding Data To Datatable
是无效演员表。正确的方法是使用 将返回的数组添加到 dt dt.Rows.Add(query.ToArray().OrderByDescending(p=>p.Activity.DateCreated).toArray());。
您可以在将数据添加到数据表中找到更多信息
回答by MBen
If the return type of OrderByDescendingwasDataTablethen the cast is not needed. The compiler knows the type of the method return type at compile time.
如果返回类型OrderByDescending是，DataTable则不需要强制转换。编译器在编译时知道方法返回类型的类型。
However OrderByDescendingdoesn't return a DataTableYou need to construct it.
但是OrderByDescending不返回 aDataTable您需要构造它。
回答by Moriya
OrderByDescending() returns an IEnumerable not a DataTable
OrderByDescending() 返回一个 IEnumerable 而不是 DataTable
This link answers what seems to be the same question. LINQ to DataTable Easy and Fast
此链接回答了似乎是同一个问题。 LINQ to DataTable 简单快速
