C#对IQueryable<T>、IEnumerable<T>的扩展方法
2024-10-06 18:46:54
#region IQueryable<T>的扩展方法
#region 根据第三方条件是否为真是否执行指定条件的查询
/// <summary>
/// 根据第三方条件是否为真是否执行指定条件的查询
/// </summary>
/// <typeparam name="T">动态类型</typeparam>
/// <param name="source">要查询的数据源</param>
/// <param name="where">条件</param>
/// <param name="condition">第三方条件</param>
/// <returns>查询的结果</returns>
public static IQueryable<T> WhereIf<T>(this IQueryable<T> source, Expression<Func<T, bool>> where,
bool condition)
{
if (PublicHelper.CheckArgument(where, "where"))
{
return condition ? source.Where(where) : source;
}
return null;
}
#endregion
#region 把IQueryable<T>集合按照指定的属性与排序方式进行排序
/// <summary>
/// 把IQueryable集合按照指定的属性与排序方式进行排序
/// </summary>
/// <typeparam name="T">数据集类型</typeparam>
/// <param name="source">要排序的数据集</param>
/// <param name="propName">要排序的属性名称</param>
/// <param name="listSort">排序方式</param>
/// <returns>返回排序后的结果集</returns>
public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> source, string propName,
ListSortDirection listSort = ListSortDirection.Ascending)
{
if (PublicHelper.CheckArgument(propName, "propName"))
{
return QueryableHelper<T>.OrderBy(source, propName, listSort);
}
return null;
}
#endregion
#region 把IQueryable<T>集合按照指定的属性与排序方式进行排序
/// <summary>
/// 把IQueryable集合按照指定的属性与排序方式进行排序
/// </summary>
/// <typeparam name="T">数据集类型</typeparam>
/// <param name="source">要排序的数据集</param>
/// <param name="sortCondition">排序条件</param>
/// <returns>返回排序后的结果集</returns>
public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> source, PropertySortCondition sortCondition)
{
if (PublicHelper.CheckArgument(sortCondition, "sortCondition"))
{
return source.OrderBy(sortCondition.PropertyName, sortCondition.ListSortDirection);
}
return null;
}
#endregion
#region 把IOrderedQueryable<T>集合按照指定的属性与排序方式进行再排序
/// <summary>
/// 把IOrderedQueryable集合按照指定的属性与排序方式进行排序
/// </summary>
/// <typeparam name="T">数据集类型</typeparam>
/// <param name="source">要排序的数据集</param>
/// <param name="propName">要排序的属性名称</param>
/// <param name="listSort">排序方式</param>
/// <returns>返回排序后的结果集</returns>
public static IOrderedQueryable<T> ThenBy<T>(this IOrderedQueryable<T> source, string propName,
ListSortDirection listSort = ListSortDirection.Ascending)
{
if (PublicHelper.CheckArgument(propName, "propName"))
{
return QueryableHelper<T>.ThenBy(source, propName, listSort);
}
return null;
}
#endregion
#region 把IOrderedQueryable<T>集合按照指定的属性与排序方式进行再排序
/// <summary>
/// 把IOrderedQueryable集合按照指定的属性与排序方式进行排序
/// </summary>
/// <typeparam name="T">数据集类型</typeparam>
/// <param name="source">要排序的数据集</param>
/// <param name="sortCondition">排序条件</param>
/// <returns>返回排序后的结果集</returns>
public static IOrderedQueryable<T> ThenBy<T>(this IOrderedQueryable<T> source, PropertySortCondition sortCondition)
{
if (PublicHelper.CheckArgument(sortCondition, "sortCondition"))
{
return QueryableHelper<T>.ThenBy(source, sortCondition.PropertyName, sortCondition.ListSortDirection);
}
return null;
}
#endregion
#region 多条件排序分页查询
/// <summary>
/// 把IQueryable集合按照指定的属性与排序方式进行排序后，再按照指定的条件提取指定页码指定条目数据
/// </summary>
/// <typeparam name="T">动态类型</typeparam>
/// <param name="source">要排序的数据集</param>
/// <param name="where">检索条件</param>
/// <param name="pageIndex">索引</param>
/// <param name="pageSize">页面大小</param>
/// <param name="total">总页数</param>
/// <param name="sortConditions">排序条件</param>
/// <returns>子集</returns>
public static IQueryable<T> Where<T>(this IQueryable<T> source, Expression<Func<T, bool>> where, int pageIndex,
int pageSize, out int total, params PropertySortCondition[] sortConditions) where T : class, new()
{
IQueryable<T> temp = null;
int i = 0;
if (PublicHelper.CheckArgument(source, "source")
&& PublicHelper.CheckArgument(where, "where")
&& PublicHelper.CheckArgument(pageIndex, "pageIndex")
&& PublicHelper.CheckArgument(pageSize, "pageSize")
&& PublicHelper.CheckArgument(sortConditions, "sortConditions"))
{
//判断是不是首个排序条件
int count = 0;
//得到满足条件的总记录数
i = source.Count(where);
//对数据源进行排序
IOrderedQueryable<T> orderSource = null;
foreach (PropertySortCondition sortCondition in sortConditions)
{
orderSource = count == 0
? source.OrderBy(sortCondition.PropertyName, sortCondition.ListSortDirection)
: orderSource.ThenBy(sortCondition.PropertyName, sortCondition.ListSortDirection);
count++;
}
source = orderSource;
temp = source != null
? source.Where(where).Skip((pageIndex - 1) * pageSize).Skip(pageSize)
: Enumerable.Empty<T>().AsQueryable();
}
total = i;
return temp;
//PublicHelper.CheckArgument(source, "source");
//PublicHelper.CheckArgument(where, "where");
//PublicHelper.CheckArgument(pageIndex, "pageIndex");
//PublicHelper.CheckArgument(pageSize, "pageSize");
//PublicHelper.CheckArgument(sortConditions, "sortConditions");
////判断是不是首个排序条件
//int count = 0;
////得到满足条件的总记录数
//total = source.Count(where);
////对数据源进行排序
//IOrderedQueryable<T> orderSource = null;
//foreach (PropertySortCondition sortCondition in sortConditions)
//{
// orderSource = count == 0
// ? source.OrderBy(sortCondition.PropertyName, sortCondition.ListSortDirection)
// : orderSource.ThenBy(sortCondition.PropertyName, sortCondition.ListSortDirection);
// count++;
//}
//source = orderSource;
//return source != null
// ? source.Where(where).Skip((pageIndex - 1) * pageSize).Skip(pageSize)
// : Enumerable.Empty<T>().AsQueryable();
}
#endregion
#region 多条件排序查询
///// <summary>
///// 多条件排序查询
///// </summary>
///// <typeparam name="T">动态类型</typeparam>
///// <param name="source">要排序的数据集</param>
///// <param name="where">检索条件</param>
///// <param name="sortConditions">排序条件</param>
///// <returns>子集</returns>
//public static IQueryable<T> Where<T>(this IQueryable<T> source, Expression<Func<T, bool>> where, params PropertySortCondition[] sortConditions) where T : class, new()
//{
// log = LogManager.GetLogger(string.Format("查询表_{0}", typeof(T)));
// IQueryable<T> temp = null;
// Logger("", () =>
// {
// if (PublicHelper.CheckArgument(source, "source")
// && PublicHelper.CheckArgument(where, "where")
// && PublicHelper.CheckArgument(sortConditions, "sortConditions"))
// {
// //判断是不是首个排序条件
// int count = 0;
// //对数据源进行排序
// IOrderedQueryable<T> orderSource = null;
// foreach (PropertySortCondition sortCondition in sortConditions)
// {
// orderSource = count == 0
// ? source.OrderBy(sortCondition.PropertyName, sortCondition.ListSortDirection)
// : orderSource.ThenBy(sortCondition.PropertyName, sortCondition.ListSortDirection);
// count++;
// }
// source = orderSource;
// temp = source != null
// ? source.Where(where)
// : Enumerable.Empty<T>().AsQueryable();
// }
// });
// return temp;
//}
#endregion
#endregion
#region IEnumerable<T>的扩展方法
#region 将集合展开分别转换成字符串，再以指定分隔字符串链接，拼成一个字符串返回
/// <summary>
/// 将集合展开分别转换成字符串，再以指定分隔字符串链接，拼成一个字符串返回
/// </summary>
/// <typeparam name="T">动态类型</typeparam>
/// <param name="collection">要处理的集合</param>
/// <param name="separator">分隔符</param>
/// <returns>拼接后的字符串</returns>
public static string ExpandAndToString<T>(this IEnumerable<T> collection, string separator)
{
List<T> source = collection as List<T> ?? collection.ToList();
if (source.IsEmpty())
{
return "";
}
string result = source.Cast<object>()
.Aggregate<object, string>(null, (current, o) => current + String.Format("{0}{1}", o, separator));
return result.Substring(0, result.LastIndexOf(separator, StringComparison.Ordinal));
}
#endregion
#region 根据指定条件返回集合中不重复的元素
/// <summary>
/// 根据指定条件返回集合中不重复的元素
/// </summary>
/// <typeparam name="T">动态类型</typeparam>
/// <typeparam name="TKey">动态筛选条件类型</typeparam>
/// <param name="source">要操作的数据源</param>
/// <param name="keySelector">重复数据的筛选条件</param>
/// <returns>不重复元素的集合</returns>
public static IEnumerable<T> DistinctBy<T, TKey>(this IEnumerable<T> source, Func<T, TKey> keySelector)
{
//取分组集合中每组的第一条数据
return source.GroupBy(keySelector).Select(group => group.First());
}
#endregion
#region 根据第三方条件是否为真是否执行指定条件的查询
/// <summary>
/// 根据第三方条件是否为真是否执行指定条件的查询
/// </summary>
/// <typeparam name="T">动态类型</typeparam>
/// <param name="source">要查询的数据源</param>
/// <param name="where">条件</param>
/// <param name="condition">第三方条件</param>
/// <returns>查询的结果</returns>
public static IEnumerable<T> WhereIf<T>(this IEnumerable<T> source, Func<T, bool> where,
bool condition)
{
return condition ? source.Where(where) : source;
}
#endregion
#region 判断集合是否为空
/// <summary>
/// 判断集合是否为空
/// </summary>
/// <typeparam name="T">动态类型</typeparam>
/// <param name="collection">要处理的集合</param>
/// <returns>集合为空返回true 不为空返回false</returns>
public static bool IsEmpty<T>(this IEnumerable<T> collection)
{
return !collection.Any();
}
#endregion
#endregion
#region 其他
/// <summary>
/// 扩展Between 操作符
/// 使用 var query = db.People.Between(person => person.Age, 18, 21);
/// </summary>
/// <typeparam name="TSource"></typeparam>
/// <typeparam name="TKey"></typeparam>
/// <param name="source">当前值</param>
/// <param name="keySelector">拉姆达表达式</param>
/// <param name="low">低</param>
/// <param name="high">高</param>
/// <returns></returns>
public static IQueryable<TSource> Between<TSource, TKey>(this IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector, TKey low, TKey high) where TKey : IComparable<TKey>
{
Expression key = Expression.Invoke(keySelector, keySelector.Parameters.ToArray());
Expression lowerBound = Expression.GreaterThanOrEqual(key, Expression.Constant(low));
Expression upperBound = Expression.LessThanOrEqual(key, Expression.Constant(high));
Expression and = Expression.AndAlso(lowerBound, upperBound);
Expression<Func<TSource, bool>> lambda = Expression.Lambda<Func<TSource, bool>>(and, keySelector.Parameters);
return source.Where(lambda);
}
/// <summary>
/// In
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="value"></param>
/// <param name="values"></param>
/// <returns></returns>
public static bool In<T>(this T value, params T[] values)
{
return values.Contains(value);
}
/// <summary>
/// Between
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="i"></param>
/// <param name="start"></param>
/// <param name="end"></param>
/// <returns></returns>
public static bool Between<T>(this T i, T start, T end) where T : IComparable<T>
{
return i.CompareTo(start) >= 0 && i.CompareTo(end) <= 0;
}
/// <summary>
/// And
/// </summary>
/// <param name="left"></param>
/// <param name="right"></param>
/// <returns></returns>
public static bool And(this bool left, bool right)
{
return left && right;
}
/// <summary>
/// Or
/// </summary>
/// <param name="left"></param>
/// <param name="right"></param>
/// <returns></returns>
public static bool Or(this bool left, bool right)
{
return left || right;
}
#endregion
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