LINQ in Business Layer paging / sorting gridview in User layer

Question

I have a gridview in my user layer that uses a business layer method as its datasource, and I want the gridview to support paging and sorting. When I returned an Ienumerable from the method, it will bring back all of the data. If I use Take/Skip to bring back only a page's worth, the gridview doesn't realize that there are many pages of data.

When I change the Ienumerable to an IQueryable, the DataBind() fails because the data has already been disposed of. I think this problem has something to do with when the query actually executes and it may have to do with the filters I am applying to the query (see below).

User Layer Code:

grdSelectedQuestionaires.DataSource = assessment.FilteredAssessmentList(filter);
grdSelectedQuestionaires.DataBind(); <-- Fails - "Cannot access a disposed object"

Business Layer Code:

public IQueryable<Assessment> FilteredAssessmentList(AssessmentSearchFilter filter)
    {
        using (PAQcDataLayerDataContext dc = new PAQcDataLayerDataContext())
        {
            var rows = (
                    from a in dc.vPAQSummaries
                    select new Assessment()
                    {
                        PAQNumber = a.PAQNumber.Trim(),
                        CustomerID = (int)a.CustomerID,
                        Department = a.Department.Trim(),
                        CustomerName = a.CustomerName.Trim(),
                        DOTNumber = a.DOTNumber.Trim(),
                        OrgName = a.OrgName.Trim(),
                        DateEntered = a.DateEntered,
                        GroupNumber = a.GroupNumber.Trim(),
                        JobTitle = a.JobTitle.Trim(),
                        FileNames = a.FileNames.Trim(),
                        AnalystType = a.AnalystType.ToString(),
                        Incumbents = a.Incumbents,
                    });

            //  Filter by Customer ID
            if (filter.CustomerID > 0)
            {
                rows = rows.Where(r => r.CustomerID == filter.CustomerID);
            }
            else
            {
                rows = rows.Where(r => r.CustomerID != null);
            }

            //  Filter by DOT Number
            if (!string.IsNullOrEmpty(filter.DOTNumberFrom))
            {
                if (string.IsNullOrEmpty(filter.DOTNumberTo))
                {
                    rows = rows.Where(r => r.DOTNumber == filter.DOTNumberFrom);
                }
                else
                {
                    rows = rows.Where(r => r.DOTNumber.CompareTo(filter.DOTNumberFrom) >= 0
                        && r.DOTNumber.CompareTo(filter.DOTNumberTo) <= 0);
                }
            }

            //  Filter by OrgName
            if (!string.IsNullOrEmpty(filter.OrgName))
            {
                rows = rows.Where(r => r.OrgName.StartsWith(filter.OrgName));
            }

            //  Filter by Group
            if (!string.IsNullOrEmpty(filter.GroupNumberFrom))
            {
                if (!string.IsNullOrEmpty(filter.GroupNumberTo))
                {
                    rows = rows.Where(r => r.GroupNumber == filter.GroupNumberFrom);
                }
                else
                {
                    rows = rows.Where(r => r.GroupNumber.CompareTo(filter.GroupNumberFrom) >= 0
                        && r.GroupNumber.CompareTo(filter.GroupNumberTo) <= 0);
                }
            }

            if (filter.Skip > 0)
            {
                rows = rows.Skip(filter.Skip);
            }
            if (filter.Take > 0)
            {
                rows = rows.Take(filter.Take);
            }
            else
            {
                rows = rows.Take(100);
            }

            return rows.Distinct();
        }
    }
}

Answer 1

The paging problem was caused by the Using statement. Changing this:

using (PAQcDataLayerDataContext dc = new PAQcDataLayerDataContext())
{
...
}

to this:

PAQcDataLayerDataContext dc = new PAQcDataLayerDataContext();

Made paging work. Now I have to figure out how sorting works.