MvcContrib Grid Sorting on complex object

问题:

I am trying to work with MvcContrib Grid control. But I cannot seem to get the sorting to work on complex objects that hold other objects.

I have setup my controller/classes/Views similar to the OP in this question. Sorting with MVCContrib

I have tried to use the SortColumnName to my childobject.property but it gives me an error saying My main object does not have this property. This is my code snippet

//POCO class

class Issue {
   public int ID {get; get; }
   .....
   public int priorityId {get; set;}
   public virtual Priority priority {get; set;}
}

//Controller code

    public ViewResult Index(int? pageNo, GridSortOptions sort)
    {
        var issues = db.issues.Include(i => i.priority);
        ViewBag.sort = sort; 

        if (!string.IsNullOrEmpty(sort.Column))
        {
            issues = issues.OrderBy(sort.Column, sort.Direction);
        }
        return View(issues.ToList().AsPagination(pageNo ?? 1, 10));
    }

//View code for the Grid

@Html.Grid(Model).Sort(ViewBag.sort as GridSortOptions).Columns(column => {
    column.For(issue => Html.ActionLink(" ", "Edit", new { id = issue.ID, areas = "Issues", controller = "Main"}, new { @id="editBtn"})).Named("Edit");
    column.For(issue => Html.ActionLink(issue.ID.ToString(), "Edit", new {id = issue.ID, areas = "Issues", controller = "Main"})).Named("ID").Sortable(true);
     column.For(issue => issue.priority.codeDesc).Named("Priority").SortColumnName("priority.codeDesc").Sortable(true);
}).Empty("No data found")

When I try to sort on the priority string, it gives me an error saying 'priority.codeDesc is not a property of Issue'.

TIA

回答1:

The issue here isn't actually related to the grid, but rather to the .OrderBy extension method provided as part of the MvcContrib sorting extensions. This extension is fairly simplistic and I only wrote it to cover simple cases where you want to sort on a direct property of the object, however in your case you're trying to order on a nested property ("priority.codeDesc") which isn't supported - you can't use dot notation with this extension.

You'd either need to switch to using a different mechanism to perform the actual sorting, or if this is a one-off situation then you could hard-code the sorting logic for this particular column (not ideal, but if it's a one off then it's simpler than writing a new sorting mechanism), eg:

if (!string.IsNullOrEmpty(sort.Column))
{
    if(sort.Column == "priority.codeDesc") 
    {
        issues = issues.OrderBy(x => x.priority.codeDesc);
    } 
    else
    {
        issues = issues.OrderBy(sort.Column, sort.Direction);
    }
}

回答2:

OMG! Dots!

I was in the same boat but thanks God I found a brilliant solution posted by our fellow developer Jarrett Meyer. I found it after maybe 3 hours Googling in the past and just now when I decided to boost my pagination and sorting with MvcContrib Grid.

You can find the full post here:

Server-Side Sorting With Dynamic LINQ

His code saved me... :D The use of LINQ's Aggregate function was AWESOME! Kudozzz to him.

I had to change Jarretts' original code a little bit to fit it to my needs. Here's the code after I modified it:

public static IQueryable<T> OrderBy<T>(this IQueryable<T> collection, GridSortOptions sortOptions)
{
    if (string.IsNullOrEmpty(sortOptions.Column))
    {
        return collection;
    }

    Type collectionType = typeof(T);

    ParameterExpression parameterExpression = Expression.Parameter(collectionType, "p");

    Expression seedExpression = parameterExpression;

    Expression aggregateExpression = sortOptions.Column.Split('.').Aggregate(seedExpression, Expression.Property);

    MemberExpression memberExpression = aggregateExpression as MemberExpression;

    if (memberExpression == null)
    {
        throw new NullReferenceException(string.Format("Unable to cast Member Expression for given path: {0}.", sortOptions.Column));
    }

    LambdaExpression orderByExp = Expression.Lambda(memberExpression, parameterExpression);

    const string orderBy = "OrderBy";

    const string orderByDesc = "OrderByDescending";

    Type childPropertyType = ((PropertyInfo)(memberExpression.Member)).PropertyType;

    string methodToInvoke = sortOptions.Direction == MvcContrib.Sorting.SortDirection.Ascending ? orderBy : orderByDesc;

    var orderByCall = Expression.Call(typeof(Queryable), methodToInvoke, new[] { collectionType, childPropertyType }, collection.Expression, Expression.Quote(orderByExp));

    return collection.Provider.CreateQuery<T>(orderByCall);
}

Now you can call this extension method like this in your controller method:

var users = Database.Memberships.OrderBy(sort);

where sort is GridSortOptions that lives in MvcContrib.UI.Grid.

sort.ColumnName can contain strings like these ones now:

User.UserName
User.MyRelatedEntity.RelatedEntityProperty
User.MyRelatedEntity.RelatedEntityProperty.AndSoON 

Note that when you create your Grid columns you can specify

.SortColumnName("User.UserName")