业务层的LINQ分页/用户层的排序gridview

Question

我的用户层中有一个gridview，它使用业务层方法作为其数据源，并且我希望gridview支持分页和排序。当我从该方法返回一个 Ienumerable 时，它将带回所有数据。如果我使用 Take/Skip 只返回一页的值，则 gridview 不会意识到有很多页的数据。

当我将 Ienumerable 更改为 IQueryable 时，DataBind() 失败，因为数据已被处理。我认为这个问题与查询实际执行的时间有关，并且可能与我应用于查询的过滤器有关（见下文）。

用户层代码：

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

业务层代码：

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

分页问题是由Using语句引起的。改变这个：

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

对此：

PAQcDataLayerDataContext dc = new PAQcDataLayerDataContext();

使分页工作。现在我必须弄清楚排序是如何工作的。