public static IQueryable <T> Query <T>(this IQueryable <T> data, QueryDescriptor descriptor, out int totalPages)
{
totalPages = 0;
var parser = new QueryExpressionParser <T>();
//filter
var filter = parser.Parse(descriptor);
var result = data.Where(filter);
//order
if (descriptor.OrderBy != null)
{
Type type = typeof(T);
var parameter = Expression.Parameter(type);
var propertyInfo = type.GetProperty(descriptor.OrderBy.Key);
Expression propertySelector = Expression.Property(parameter, propertyInfo);
//To deal with different type of the property selector, very hacky
//looking for a better solution
if (propertyInfo.PropertyType == typeof(string))
{
var orderby = Expression.Lambda <Func <T, string> >(propertySelector, parameter);
if (descriptor.OrderBy.Order == OrderSequence.DESC)
{
result = result.OrderByDescending(orderby);
}
else
{
result = result.OrderBy(orderby);
}
}
else if (propertyInfo.PropertyType == typeof(decimal))
{
var orderby = Expression.Lambda <Func <T, decimal> >(propertySelector, parameter);
if (descriptor.OrderBy.Order == OrderSequence.DESC)
{
result = result.OrderByDescending(orderby);
}
else
{
result = result.OrderBy(orderby);
}
}
else if (propertyInfo.PropertyType == typeof(int))
{
var orderby = Expression.Lambda <Func <T, int> >(propertySelector, parameter);
if (descriptor.OrderBy.Order == OrderSequence.DESC)
{
result = result.OrderByDescending(orderby);
}
else
{
result = result.OrderBy(orderby);
}
}
else if (propertyInfo.PropertyType == typeof(double))
{
var orderby = Expression.Lambda <Func <T, double> >(propertySelector, parameter);
if (descriptor.OrderBy.Order == OrderSequence.DESC)
{
result = result.OrderByDescending(orderby);
}
else
{
result = result.OrderBy(orderby);
}
}
else if (propertyInfo.PropertyType == typeof(float))
{
var orderby = Expression.Lambda <Func <T, float> >(propertySelector, parameter);
if (descriptor.OrderBy.Order == OrderSequence.DESC)
{
result = result.OrderByDescending(orderby);
}
else
{
result = result.OrderBy(orderby);
}
}
}
//paging
if (descriptor.PageSize > 0)
{
int totalCount = result.Count();
totalPages = totalCount % descriptor.PageSize == 0 ? totalCount / descriptor.PageSize : totalCount / descriptor.PageSize + 1;
return(result.Skip((descriptor.PageIndex - 1) * descriptor.PageSize).Take(descriptor.PageSize));
}
return(result);
}
public static IQueryable <T> Query <T>(this IQueryable <T> data, QueryDescriptor descriptor)
{
int totalPages = 0;
return(Query <T>(data, descriptor, out totalPages));
}