lambda expression in asp.net MVC

Question

I am trying to select specific columns from a model but getting an error when I try to include select for the child entity. My model is -

public class Alert
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid AlertId { get; set; }

    [Display(Name = "Title"), MaxLength(160, ErrorMessage ="Title cannot be more than 200 characters long."), Required(ErrorMessage ="You must enter an alert title")]
   // [DataType(DataType.MultilineText)]
    public string Title { get; set; }


    [Display(Name = "Description"), MaxLength(8000, ErrorMessage = "Title cannot be more than 8000 characters long."), Required(ErrorMessage ="You must enter a description in {0} field")]
    [AllowHtml]
    [DataType(DataType.MultilineText)]
    public string Description { get; set; }

   [Display(Name = "Start Date"), Required(ErrorMessage ="You must enter the start date and time")]
   [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy hh:mm tt}", ApplyFormatInEditMode = false)]
  // [DataType(DataType.DateTime)]
    public DateTime StartDate { get; set; }

    [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy hh:mm tt}", ApplyFormatInEditMode = false)]
    [Display(Name = "End Date")]
    public DateTime? EndDate { get; set; }

    [Display(Name = "Affected Site/s"), MaxLength(200,ErrorMessage ="You cannot enter more than 200 characters.")]
    public string SitesAffected { get; set; }


    [MaxLength(10)]
    public string Published { get; set; }

    [Display(Name = "Website Link"), MaxLength(200,ErrorMessage ="This cannot be more than 200 characters.")]
    public string WebLink { get; set; }


    [Display(Name ="Alert Type")]
    public int AId { get; set; }

    public virtual ICollection<Location> Location { get; set; }
    public virtual ICollection<AlertFile> Files { get; set; }
    [JsonIgnore]
    public virtual AlertType alertType {get; set;}

}

I can use the following lambda expression to produce json data through Web API.

var alerts = db.Alerts.Where(a=>a.alertType.Slug== alert && a.EndDate>=DateTime.Now && a.Published=="Yes").Select(s=>new
        {s.Title, s.Description, s.alertType.Slug, s.StartDate, s.EndDate, s.Location
        });


        return Request.CreateResponse(HttpStatusCode.OK, alerts.ToList());

The above code displays all the columns from the location table. I want to display specific columns from the location table and I tried the following code but getting error.

var alerts = db.Alerts.Where(a=>a.alertType.Slug== alert && a.EndDate>=DateTime.Now && a.Published=="Yes").Select(s=>new
        {s.Title, s.Description, s.alertType.Slug, s.StartDate, s.EndDate, s.Location.Select(l => new Location { l.Name, l.Latitude, l.Longitude, l.ParkId, l.Contact })
        });

Error: Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access.

Basically location is not allowing me to use select clause. Can anyone please help with this. Thanks in advance.

Invalid anonymous type member declarator. Anonymous type members must be declared with a member assignment, simple name or member access. — Tajuddin
– Tajuddin, Commented Dec 6, 2016 at 7:34
locations = s.Location.Select(l => new { l.Name, l.Latitude, ... }) — user3559349
– user3559349, Commented Dec 6, 2016 at 7:37

teo van kot · Accepted Answer · 2016-12-06 07:48:10Z

With this line:

s.Location.Select(l => new Location { l.Name, l.Latitude, l.Longitude, l.ParkId, l.Contact }

You don't assign your values to any property, you just select it if you want to assign your selected list to property like @Stephen Muecke said you should write:

Location = s.Location.Select(l => new Location { l.Name, l.Latitude, l.Longitude, l.ParkId, l.Contact }

Actually your full query should look like this:

var alerts = db.Alerts.Where(a=>a.alertType.Slug== alert && a.EndDate>=DateTime.Now && a.Published=="Yes").Select(s=>new
        { 
            Title = s.Title, 
            Description = s.Description, 
            AlertType = s.alertType.Slug, 
            StartDate = s.StartDate, 
            EndDate = s.EndDate, 
            Location = s.Location.Select(l => new Location { l.Name, l.Latitude, l.Longitude, l.ParkId, l.Contact })
        });

But C# compiler know how to name simple properties.

Christoph Fink · Accepted Answer · 2016-12-06 07:42:56Z

2

You need to name your property in the anonymous type:

var alerts = db.Alerts.Where(a=>a.alertType.Slug== alert && a.EndDate>=DateTime.Now && a.Published=="Yes").Select(s=>new
    {
      s.Title, s.Description, s.alertType.Slug, s.StartDate, s.EndDate,
      location = s.Location.Select(l => new Location { l.Name, l.Latitude, l.Longitude, l.ParkId, l.Contact })
    });

If you just select a simple property the name of the property is used automatically, but for other selects you need to name it on your own.

answered Dec 6, 2016 at 7:42

Christoph Fink

23.2k9 gold badges72 silver badges118 bronze badges

Comments

Tajuddin · Accepted Answer · 2016-12-06 07:43:36Z

0

In case if you someone has the same issue. I have changed the lambda expression to the following as Stephen suggested. It works fine now.

var alerts = db.Alerts.Where(a=>a.alertType.Slug== alert && a.EndDate>=DateTime.Now && a.Published=="Yes").Select(s=>new
        {s.Title, s.Description, s.alertType.Slug, s.StartDate, s.EndDate, locations= s.Location.Select(l => new { l.Name, l.Latitude, l.Longitude, l.ParkId, l.Contact })
        });

answered Dec 6, 2016 at 7:43

Tajuddin

733 silver badges13 bronze badges

Collectives™ on Stack Overflow

lambda expression in asp.net MVC

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related