/// <summary>
/// Deletes all entities from the table of the specified type
/// </summary>
/// <typeparam name="T">Entity of type T</typeparam>
/// <typeparam name="DT">Your DbContext type</typeparam>
public static void DeleteAll <T, DT>() where DT : DbContext where T : class
{
DT db = DBContextFactory.GetDbContext <DT>();
DbSet <T> dbSet = db.Set <T>();
dbSet.RemoveRange(dbSet);
db.SaveChanges();
}
/// <summary>
/// Note that there are no async versions of some LINQ operators such as Where or OrderBy,
/// because these only build up the LINQ expression tree and don't cause the query to be executed in the database.
/// Only operators which cause query execution have async counterparts.
/// </summary>
/// <typeparam name="T">Type of entity you are querying</typeparam>
/// <typeparam name="DT">Type of DbContext the entity is from</typeparam>
/// <param name="Pager">A EFPager that simplifies paging through the entity table</param>
/// <returns>A page of IQueryable sorted data of type T</returns>
public static async Task <IQueryable <T> > QueryEntities <T, DT>(EFPager <T> Pager) where DT : DbContext where T : class
{
DT db = DBContextFactory.GetDbContext <DT>();
DbSet <T> dbSet = db.Set <T>();
IQueryable <T> filteredSet = dbSet; // (from x in dbSet select x);
if (Pager.WhereClause != null)
{
filteredSet = filteredSet.Where(Pager.WhereClause);
}
IOrderedQueryable <T> ordered = null;
// Apply all column sorting one at a time. We are simply modifying
// the expression tree. No data is actually coming from the DB yet!
foreach (ColumnSortInfo <T> sortColumn in Pager.SortOrder)
{
if (ordered == null)
{
if (sortColumn.SortAscending)
{
ordered = filteredSet.OrderBy(sortColumn.ColumnName);
}
else
{
ordered = filteredSet.OrderByDescending(sortColumn.ColumnName);
}
}
else
{
if (sortColumn.SortAscending)
{
ordered = ordered.ThenBy(sortColumn.ColumnName);
}
else
{
ordered = ordered.ThenByDescending(sortColumn.ColumnName);
}
}
}
if (ordered != null)
{
filteredSet = ordered;
}
// Now that our query has been fully constructed, ask the database
// how many records will be in the result. We can then calculate
// all the necessary paging information.
if (!Pager.Initialized)
{
int TotalRowCount = await filteredSet.CountAsync();
Pager.InitializePageInfo(TotalRowCount);
}
// Now ask for ONLY the page of data we are looking for
filteredSet = filteredSet.Skip(Pager.Skip).Take(Pager.PageSize);
// Update the page number so we can easily walk through a whole table
Pager.MoveToNextPage();
return(filteredSet);
}
