CODEWITHSUNDEEP
c#.netlinqasync-awaitentity-framework-6
paul deter
paul deter

Reputation: 857

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

I would like to wait for this query before proceeding to do anything else. I have seen several question on this topic but none of those are using custom function in the query, which is making it little tricky. Is it even possible to use await with following query. I am using await-async in .NET4.0 using Microsoft Async package.(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 "";
        }

Upvotes: 2

Views: 211

Answers (2)

Servy
Servy

Reputation: 203834

You can use ToListAsync to asynchronously get the results of an EF query.

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();

Upvotes: 4

Yuval Itzchakov
Yuval Itzchakov

Reputation: 149538

You can await using ToListAsync() instead of ToList() if you invoke your first part of the query before bringing it in to memory:

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();

Upvotes: 2

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