/// <summary>
/// 判断实体是否具有孩子。
/// </summary>
/// <param name="entity">当前实体。</param>
/// <param name="predicate">用于测试每个元素是否满足条件的函数。</param>
/// <returns></returns>
public virtual bool HasChildren(TEntity entity, Expression <Func <TEntity, bool> > predicate = null)
{
var query = (IQueryable)QueryHelper.CreateQuery <TEntity>(repository.Provider, predicate);
var mthCount = typeof(Enumerable).GetMethods().FirstOrDefault(s => s.Name == "Count" && s.GetParameters().Length == 2);
mthCount = mthCount.MakeGenericMethod(typeof(TEntity));
var expression = TreeExpressionBuilder.BuildHasChildrenExpression(metaTree, entity, predicate);
expression = Expression.Call(null, mthCount, query.Expression, expression);
return((int)repository.Provider.Execute(expression) > 0);
}
/// <summary>
/// 异步的，判断实体是否具有孩子。
/// </summary>
/// <param name="entity">当前实体。</param>
/// <param name="predicate">用于测试每个元素是否满足条件的函数。</param>
/// <param name="cancellationToken">取消操作的通知。</param>
/// <returns></returns>
public virtual async Task <bool> HasChildrenAsync(TEntity entity, Expression <Func <TEntity, bool> > predicate = null, CancellationToken cancellationToken = default)
{
var query = (IQueryable)QueryHelper.CreateQuery <TEntity>(repository.Provider, predicate);
var mthCount = typeof(Enumerable).GetMethods().FirstOrDefault(s => s.Name == "Count" && s.GetParameters().Length == 2);
mthCount = mthCount.MakeGenericMethod(typeof(TEntity));
var expression = TreeExpressionBuilder.BuildHasChildrenExpression(metaTree, entity, predicate);
expression = Expression.Call(null, mthCount, query.Expression, expression);
return(await((IAsyncQueryProvider)repository.Provider).ExecuteAsync <int>(expression, cancellationToken) > 0);
}
