public static Expression GetConstantExpression(FilterMetaRecord meta, string val)
{
if (meta.ParametrType.IsEnum)
{
return(Expression.Constant(Enum.Parse(meta.ParametrType, val)));
}
else
{
return(Expression.Constant(Convert.ChangeType(val, meta.ParametrType)));
}
}
public static Expression GetFirstExpression(FilterMetaRecord meta, Expression valExperssion, Expression propertyAccess)
{
Expression res = null;
switch (meta.OperatorName)
{
case Operators.Equal:
{
res = Expression.Equal(propertyAccess, valExperssion);
break;
}
case Operators.Contains:
{
res = Expression.Call(propertyAccess, typeof(string).GetMethod("Contains", new Type[] { typeof(string) }), valExperssion);
break;
}
}
return(res);
}
public static Expression GetNextExpression(Expression condition, FilterMetaRecord meta, Expression ValExpression, Expression propertyAccess)
{
Expression res = null;
switch (meta.OperatorBetween)
{
case Operators_between.Or:
{
res = Expression.Or(condition, GetFirstExpression(meta, ValExpression, propertyAccess));
break;
}
case Operators_between.And:
{
res = Expression.And(condition, GetFirstExpression(meta, ValExpression, propertyAccess));
break;
}
}
return(res);
}
public static IQueryable <T> FilterByFilterMetaRecord <T>(IQueryable <T> items, FilterRecord filter, FilterMetaRecord meta)
{
var param = Expression.Parameter(typeof(T), "x");
var propertyAccess = meta.Path.Split('.').Aggregate((Expression)param, Expression.Property);
var constValue = GetConstantExpression(meta, filter.Value[0]);
var condition = GetFirstExpression(meta, constValue, propertyAccess);
if (!meta.IsSingleFilter)
{
for (int i = 1; i < filter.Value.Count; i++)
{
var now_val_next = GetConstantExpression(meta, filter.Value[i]);
condition = GetNextExpression(condition, meta, now_val_next, propertyAccess);
}
}
return(items.Where(Expression.Lambda <Func <T, bool> >(condition, param)));
}
public static IOrderedQueryable <T> ThenSortingBySortingMetaRecord <T>(IOrderedQueryable <T> items, SortingRecord sort, FilterMetaRecord meta)
{
var param = Expression.Parameter(typeof(T), "x");
var propertyAccess = meta.Path.Split('.').Aggregate((Expression)param, Expression.Property);
if (sort.Direction == "asc")
{
return((IOrderedQueryable <T>)items.Provider.CreateQuery(Expression.Call(typeof(Queryable), "ThenBy", new Type[] { typeof(T), meta.ParametrType }, items.Expression, Expression.Lambda(propertyAccess, param))));
}
else
{
return((IOrderedQueryable <T>)items.Provider.CreateQuery(Expression.Call(typeof(Queryable), "ThenByDescending", new Type[] { typeof(T), meta.ParametrType }, items.Expression, Expression.Lambda(propertyAccess, param))));
}
}
