是否可以将 await 与使用自定义函数的查询一起使用

Question

我想等待此查询，然后再继续执行其他操作。我已经看到几个关于这个主题的问题，但没有一个在查询中使用自定义函数，这使得它有点棘手。甚至可以将 await 与以下查询一起使用。我正在使用 Microsoft Async 包在 .NET4.0 中使用 await-async。(https://www.nuget.org/packages/Microsoft.Bcl.Async/)

var Employees = 
    (from d in context.Employees
    join a in context.Address on d.ID equals a.EmployeeID
    select new 
    {
        Employee = d,
        Address = a,
    })
    .AsEnumerable() memory
    .Select(x => new Employee
    {
        Id = x.Employee.Id,
        PreferredName = GetPreferredName(x.Employee.FirstName, x.Employee.MiddleName, x.Employee.LastName, x.Employee.Alias),
        StreetAddress = x.Address.StreetAddress 
    })
    .ToList();

private string GetPreferredName(string firstName, string middleName, string lastName, string dnsName)
        {
            if (!string.IsNullOrEmpty(firstName))
            return firstName;
            else if (!string.IsNullOrEmpty(middleName))
                return middleName;
            else if (!string.IsNullOrEmpty(lastName))
                return lastName;
            else if (!string.IsNullOrEmpty(dnsName))
                return dnsName;

            return "";
        }

Answer 1

您可以 await 使用 ToListAsync() 而不是 ToList() 如果您在将查询的第一部分存入内存之前调用它：

var queryEmployees = await
(from d in context.Employees
join a in context.Address on d.ID equals a.EmployeeID
select new 
{
    Employee = d,
    Address = a,
}).ToListAsync();

var employees = Employees.Select(x => new Employee
{
    Id = x.Employee.Id,
    PreferredName = GetPreferredName(x.Employee.FirstName, x.Employee.MiddleName, x.Employee.LastName, x.Employee.Alias),
    StreetAddress = x.Address.StreetAddress 
})
.ToList();

Answer 2

您可以使用 ToListAsync 异步获取 EF 查询的结果。

var query = await
    (from d in context.Employees
    join a in context.Address on d.ID equals a.EmployeeID
    select new 
    {
        Employee = d,
        Address = a,
    })
    .ToListAsync();

var Employees = query    
    .Select(x => new Employee
    {
        Id = x.Employee.Id,
        PreferredName = GetPreferredName(x.Employee.FirstName, x.Employee.MiddleName, x.Employee.LastName, x.Employee.Alias),
        StreetAddress = x.Address.StreetAddress 
    })
    .ToList();

是否可以将 await 与使用自定义函数的查询一起使用

Is it possible to use await with query that uses custom function

c#

.net

linq

async-await

entity-framework-6