希望查询在Linq查询中按变量排序

假设您想通过SQL进行排序,那么需要传入sort列/类型。查询将推迟到您实际执行select时进行,以便您可以分步构建查询,完成后按如下方式执行:

// Do you query first.  This will NOT execute in SQL yet.
var query = lDC.tbl_Products.Where(p => p.TypeRef == pTypeId);

// Now add on the sort that you require... you could do ascending, descending,
// different cols etc..
switch (sortColumn)
{
    case "Price":
        query = query.OrderBy(q => q.Price);
        break;
    case "Code":
        query = query.OrderBy(q => q.Code);
        break;
    // etc...
}

// Now execute the query to get a result
var result = query.ToList();

如果您想在SQL之外执行此操作,那么只需获得一个基本结果,而不进行排序,然后根据您需要的排序条件对结果应用OrderBy。

    public static IEnumerable<T> OrderByIf<T,TKey>(this IEnumerable<T> source, bool condition, Func<T, TKey> keySelector)
    {
        return (condition) ? source.OrderBy(keySelector).AsEnumerable() : source;
    }

            var query = lDC.tbl_Products.Where(p => p.TypeRef == pTypeId)
                                    .OrderByIf(sortColumn == "Price", p => p.Price)
                                    .OrderByIf(sortColumn == "Code", p => p.Code);

您可以在单独的步骤中“构建”LINQ查询。

var data = from lm in lDc.tbl_Products
           where lm.TypeRef == pTypeId
           select new;

var orderedData = from lm in data
                  order lm.Code ascending
                  select new;

// TODO: Display orderedData in a grid.

您枚举的完整查询将被计算。这意味着您可以为下拉列表中的每个项目运行一个单独的查询,该查询是从“基本”查询构建的。