使用Azure的DocumentDb和.NET API,我有以下方法,非常适合检索整个文档的列表:
public async Task<IEnumerable<T>> GetItemsAsync<T>(Expression<Func<T, bool>> predicate)
{
IDocumentQuery<T> query = _Client.CreateDocumentQuery<T>(
UriFactory.CreateDocumentCollectionUri(_DatabaseId, _Collection),
new FeedOptions { MaxItemCount = -1 })
.Where(predicate)
.AsDocumentQuery();
List<T> results = new List<T>();
while (query.HasMoreResults)
{
var item = await query.ExecuteNextAsync<T>();
results.AddRange(item);
}
return results;
}
现在,我并不总是希望返回整个文档(特别是考虑到DocumentDb RU定价模型),所以我认为我应该能够像这样添加.Select投影:
public async Task<List<TResult>> GetItemsAsync<T, TResult>(Expression<Func<T, bool>> predicate, Expression<Func<T, TResult>> select)
{
IDocumentQuery<TResult> query = _Client.CreateDocumentQuery<T>(
UriFactory.CreateDocumentCollectionUri(_DatabaseId, _Collection),
new FeedOptions { MaxItemCount = -1 })
.Where(predicate)
.Select(select)
.AsDocumentQuery();
List<TResult> results = new List<TResult>();
while (query.HasMoreResults)
{
var item = await query.ExecuteNextAsync<TResult>();
results.AddRange(item);
}
return results;
}
用法:
var rez = await _docs.GetItemsAsync<ApolloAssetDoc, Guid?>(x => x.MyVal == 5, x => x.ID);
但第二种方法总是返回0结果 . 显然我正在咆哮错误的树 .
知道为选择多个属性的查询返回动态对象列表的正确方法是什么(例如 "SELECT d.id, d.MyVal FROM Items d WHERE d.DocType=0"
)或者只选择了一个属性的简单列表(例如 "SELECT d.id FROM Items d WHERE d.DocType=0"
)?
1 回答
如果实体类中的 ID 属性没有
[JsonProperty(PropertyName = "id")]
,我可以重新发出此问题 . 如果未包含,请尝试使用以下代码:Note :该字段为 case sensitive .