重构 LINQ 表达式以删除重复代码
本文关键字：代码 删除 LINQ 表达式 重构 | 更新日期: 2023-09-27 18:35:59
我有以下一段代码，我尝试重构它以删除重复的代码。但是，每次我尝试重构它时，我都会卡住。有没有人可以帮助我解决这个问题。
public static IOrderedQueryable<T> ObjectSort<T>(this IQueryable<T> entities, Expression<Func<T, object>> expression, string order = "asc")
{
var sortOrder = order == "asc" ? SortOrder.Ascending : SortOrder.Descending;
return entities.ObjectSort(expression, sortOrder);
}
public static IOrderedQueryable<T> ObjectThenBy<T>(this IOrderedQueryable<T> entities, Expression<Func<T, object>> expression, string order = "asc")
{
var sortOrder = order == "asc" ? SortOrder.Ascending : SortOrder.Descending;
return entities.ObjectThenBy(expression, sortOrder);
}
public static IOrderedQueryable<T> ObjectSort<T>(this IQueryable<T> entities, Expression<Func<T, object>> expression, SortOrder order = SortOrder.Ascending)
{
var unaryExpression = expression.Body as UnaryExpression;
if (unaryExpression != null)
{
var propertyExpression = (MemberExpression)unaryExpression.Operand;
var parameters = expression.Parameters;
if (propertyExpression.Type == typeof(DateTime))
{
var newExpression = Expression.Lambda<Func<T, DateTime>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
if (propertyExpression.Type == typeof(DateTime?))
{
var newExpression = Expression.Lambda<Func<T, DateTime?>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
if (propertyExpression.Type == typeof(int))
{
var newExpression = Expression.Lambda<Func<T, int>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
if (propertyExpression.Type == typeof(int?))
{
var newExpression = Expression.Lambda<Func<T, int?>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
if (propertyExpression.Type == typeof(bool))
{
var newExpression = Expression.Lambda<Func<T, bool>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
throw new NotSupportedException("Object type resolution not implemented for this type");
}
return order == SortOrder.Ascending ? entities.OrderBy(expression) : entities.OrderByDescending(expression);
}
public static IOrderedQueryable<T> ObjectThenBy<T>(this IOrderedQueryable<T> entities, Expression<Func<T, object>> expression, SortOrder order = SortOrder.Ascending)
{
var unaryExpression = expression.Body as UnaryExpression;
if (unaryExpression != null)
{
var propertyExpression = (MemberExpression)unaryExpression.Operand;
var parameters = expression.Parameters;
if (propertyExpression.Type == typeof(DateTime))
{
var newExpression = Expression.Lambda<Func<T, DateTime>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
}
if (propertyExpression.Type == typeof(DateTime?))
{
var newExpression = Expression.Lambda<Func<T, DateTime?>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
}
if (propertyExpression.Type == typeof(int))
{
var newExpression = Expression.Lambda<Func<T, int>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
}
if (propertyExpression.Type == typeof(int?))
{
var newExpression = Expression.Lambda<Func<T, int?>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
}
if (propertyExpression.Type == typeof(bool))
{
var newExpression = Expression.Lambda<Func<T, bool>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
}
throw new NotSupportedException("Object type resolution not implemented for this type");
}
return order == SortOrder.Ascending ? entities.ThenBy(expression) : entities.ThenByDescending(expression);
}
请注意，区别在于Orderby和ThenBy...其余的完全一样。希望有人知道重构它的方法。我试图创建一个 Func 参数来传递 OrderBy 或 ThenBy 方法。然而，我尝试的一切我都被卡住了。
OrderBy 和 ThenBy
之间的区别在于 OrderBy 期望 IQueryable，ThenBy 期望 IOrderedqueryAble。
现在要使用 OrderBy 或 ThenBy，您需要确定集合是 IQueryable 还是 IOrderedQueryAble。
之后，如果它是IQueryable，则调用OrderBy。如果它是 IOrderedQueryable，则调用 ThenBy （在强制转换为 IOrderedQueryable 之后。
重构的代码片段变为
public static IOrderedQueryable<T> ObjectSortRefactored<T>(this IQueryable<T> entities, Expression<Func<T, object>> expression, SortOrder order = SortOrder.Ascending)
{
var unaryExpression = expression.Body as UnaryExpression;
if (unaryExpression != null)
{
var propertyExpression = (MemberExpression)unaryExpression.Operand;
var parameters = expression.Parameters;
if (propertyExpression.Type == typeof(DateTime))
{
var newExpression = Expression.Lambda<Func<T, DateTime>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
if (propertyExpression.Type == typeof(DateTime?))
{
var newExpression = Expression.Lambda<Func<T, DateTime?>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
if (propertyExpression.Type == typeof(int))
{
var newExpression = Expression.Lambda<Func<T, int>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
if (propertyExpression.Type == typeof(int?))
{
var newExpression = Expression.Lambda<Func<T, int?>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
if (propertyExpression.Type == typeof(bool))
{
var newExpression = Expression.Lambda<Func<T, bool>>(propertyExpression, parameters);
return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
}
throw new NotSupportedException("Object type resolution not implemented for this type");
}
if(entities.GetType().IsAssignableFrom(typeof(IOrderedQueryable<T>)))
return order == SortOrder.Ascending ? (entities as IOrderedQueryable<T>).ThenBy(expression) : (entities as IOrderedQueryable<T>).ThenByDescending(expression);
return order == SortOrder.Ascending ? entities.OrderBy(expression) : entities.OrderByDescending(expression);
}
不过，我还没有测试上面的代码片段。