Dynamically use DisplayName as alias in Linq query from entity

Question

I have Manufacturer entity as below:

class Manufacturer
{
    [Key]
    public int Id { get; set; }

    [DisplayName("Manufacturer Code")]
    public int Code { get; set; }

    [DisplayName("Manufacturer Name")]
    public string Name { get; set; }
}

As you see every filed have DisplayName data annotations. In Normal way I select the rows of Manufacturer table by below code:

dataGridView1.DataSource = DatabaseContext.Set<Manufacturer>()
    .Select(m => new 
    {
        Id = m.Id,
        Code = m.Code,
        Name = m.Name,
    })
    .ToList();

I want to find a way that Dynamically put DisplayName as alias in Linq query.

I think I must a Method that generate the query something like:

dataGridView1.DataSource = DatabaseContext.Set<Manufacturer>()
    .Select(m => new 
    {
        Id = m.Id,
        [Manufacturer Code] = m.Code,
        [Manufacturer Name] = m.Name,
    })
    .ToList();

I could get the all DisplayName by below code:

public static Dictionary<string, string> GetEntityDisplayName(this Type type)
{
    return TypeDescriptor.GetProperties(type)
        .Cast<PropertyDescriptor>()
        .ToDictionary(p => p.Name, p => p.DisplayName);
}

But dont know how do that. Is there any way to put DisplayName as alias of Linq query dynamically?

Update: As one of answer say when use .ToList in get rows from an entity it return a list that project the model with DisplayNameAttribute, But the new thing is When create Linq query that use 2 entity, to list project the row that you exactly say in query. For example:

class Manufacturer
    {
        [Key]
        public int Id { get; set; }

        [DisplayName("Manufacturer Code")]
        public int Code { get; set; }

        [DisplayName("Manufacturer Name")]
        public string Name { get; set; }
    }

And:

class Good
{
    [Key]
    [DisplayName("ID")]
    public int Id { get; set; }

    [DisplayName("Good Name")]
    public string Name { get; set; }

    public int? ManufacturerId { get; set; }

    public virtual Manufacturer Manufacturer { get; set; }
}

And The Query:

using (AppDbContext db = new AppDbContext())
            {
                var res2 = db.Goods.Select(m => new
                {
                    Id = m.Id,
                    GoodsName = m.Name,
                    ManufacturerName = m.Manufacturer.Name,
                }).ToList();

                dataGridView1.DataSource = res2;
            }

As you see in this case, because the query have 2 name field, must declare different alias for them and its not the equal to DisplayNameAttribute in entity. Are anyone know a way to project the output list same as DisplayNameAttribute defined in entity?

Answer 1

After looking at the DataGridView source, I've seen that the datasource is bound to a collection of objects that have properties with DisplayNameAttribute on them it will display those attributes values in the column header of that property.

So, you only need to project your LINQ queries to view models or entities that have defined the attribute.

For example, I have the following code:

var listOfEntities = new List<CustomEntity>
{
      new CustomEntity {Id = 1, Name = "Name1", Value = "Value1"},
      new CustomEntity {Id = 2, Name = "Name2", Value = "Value2"},
      new CustomEntity {Id = 3, Name = "Name3", Value = "Value3"},
      new CustomEntity {Id = 4, Name = "Name4", Value = "Value4"},
};
dataGridView1.DataSource = listOfEntities;

public class CustomEntity
{
    public int Id { get; set; }
    [DisplayName("Custom name header")]
    public string Name { get; set; }
    [DisplayName("Custom name value")]
    public string Value { get; set; }
}

If you run this you will see that the column headers are those from the DisplayNameAttribute, not the properties name.

To project to view models you can use AutoMapper for automatic mapping of fields.

UPDATE

You can probably achieve this behavior using an Expando object. Let me warn you though you can not use this until you call .ToList() on your context. Because this will not translate by default to a valid SQL query.

using System.Reflection;
/*...*/
public static object ToDynamicDisplayName(object input)
{
    var type = input.GetType();
    dynamic dObject = new ExpandoObject();
    var dDict = (IDictionary<string, object>)dObject;

    foreach (var p in type.GetProperties())
    {
        var prop = type.GetProperty(p.Name);
        var displayNameAttr = p.GetCustomAttribute<DisplayNameAttribute>(false);
        if (prop == null || prop.GetIndexParameters().Length != 0) continue;
        if (displayNameAttr != null)
        {
            dDict[displayNameAttr.DisplayName] = prop.GetValue(input, null);
        }
        else
            dDict[p.Name] = prop.GetValue(input, null);
    }
    return dObject;
}

To use it try it like this:

var myDynamicCollection = DatabaseContext.Set<Manufacturer>().ToList().Select(m => 
                          ToDynamicDisplayName(m));

UPDATE 2

Of course I've ran the code and built successfully. My set-up is VS2017 with .NET 4.6.2. But, I've also created a .Net Fiddle for it, it's available here.