c# winforms，在搜索中使用异步和等待 function

Question

I'am trying to search employees by using async and await with button function, but my code doesn't work as my expect and get error like "requires a receiver of type 'IQueryable'". How should I do if I want to use async await in windows form. Here is my code: Thank you in advance!

  private async void btnSearch_Click(object sender, EventArgs e)
{
    using(db)
    {
        var employees = db.Analys
            .Where(x => x.Status == true)
            .Select(a => new { a.UserId, a.FirstName, a.LastName, a.DOB, a.Department,  a.DepartmentId })
            .AsEnumerable()
            .Select(b => new {
                UserId = b.UserId,
                FirstName = b.FirstName,
                LastName = b.LastName,
                Age = CalculateAge(b.DOB.ToString()),   
                Department = b.Department.DepartmenName, 
            });
            var data = await employees.ToListAsync();
            if (data!= null)
            {
                dgvEmployees.DataSource = data;           
            }    
    }

}   

Answer 1

Can you please add full error text? But from the code you've already provided I assume you are using Entity Framework to access your DB, so AsEnumerable() should already have materialized the data fetching it from db. I would say that you don't need it here, and first Select clause too. Try something like this:

  var employees = await db.Analys
        .Where(x => x.Status == true)
        .Select(b => new {
            UserId = b.UserId,
            FirstName = b.FirstName,
            LastName = b.LastName,
            Age = CalculateAge(b.DOB.ToString()),   
            Department = b.Department.DepartmenName, 
        })
        .ToListAsync();

Also the null check should not be needed here, cause EF should return empty collection.