查询文档(.NET)
DocumentDB 支持对存储在每个集合中的 JSON 文档的丰富查询。 ****
使用 LINQ 查询
IQueryable<Family> familyQuery = this.client.CreateDocumentQuery<Family>(
UriFactory.CreateDocumentCollectionUri(databaseName, collectionName), queryOptions)
.Where(f => f.LastName == "Andersen");
使用 SQL 查询
IQueryable<Family> familyQueryInSql = this.client.CreateDocumentQuery<Family>(
UriFactory.CreateDocumentCollectionUri(databaseName, collectionName),
"SELECT * FROM Family WHERE Family.lastName = 'Andersen'",
queryOptions);
LINQ 查询的分页
所述 FeedOptions 被用于设置 RequestContinuation 在第一查询获得的属性:
public async Task<IEnumerable<Family>> QueryWithPagination(int Size_of_Page)
{
var queryOptions = new FeedOptions() { MaxItemCount = Size_of_Page };
string continuationToken = string.Empty;
do
{
if (!string.IsNullOrEmpty(continuationToken))
{
queryOptions.RequestContinuation = continuationToken;
}
IDocumentQuery<Family> familyQuery = this.client.CreateDocumentQuery<Family>(
UriFactory.CreateDocumentCollectionUri(databaseName, collectionName), queryOptions)
.Where(f => f.LastName == "Andersen").AsDocumentQuery();
var queryResult = await familyQuery.ExecuteNextAsync<Family>();
continuationToken = queryResult.ResponseContinuation;
yield return queryResult;
} while (!string.IsNullOrEmpty(continuationToken));
}
你始终可以调用一次并将 Continuation Token 返回给客户端,以便在客户端需要下一页时发送分页请求。使用帮助程序类和扩展名:
public class PagedResults<T>
{
public PagedResults()
{
Results = new List<T>();
}
public string ContinuationToken { get; set; }
public List<T> Results { get; set; }
}
public async Task<PagedResults<Family>> QueryWithPagination(int Size_of_Page, string continuationToken = "")
{
var queryOptions = new FeedOptions() { MaxItemCount = Size_of_Page };
if (!string.IsNullOrEmpty(continuationToken))
{
queryOptions.RequestContinuation = continuationToken;
}
return await familyQuery = this.client.CreateDocumentQuery<Family>(
UriFactory.CreateDocumentCollectionUri(databaseName, collectionName), queryOptions)
.Where(f => f.LastName == "Andersen").ToPagedResults();
}
public static class DocumentDBExtensions
{
public static async Task<PagedResults<T>> ToPagedResults<T>(this IQueryable<T> source)
{
var documentQuery = source.AsDocumentQuery();
var results = new PagedResults<T>();
try
{
var queryResult = await documentQuery.ExecuteNextAsync<T>();
if (!queryResult.Any())
{
return results;
}
results.ContinuationToken = queryResult.ResponseContinuation;
results.Results.AddRange(queryResult);
}
catch
{
//documentQuery.ExecuteNextAsync throws an exception on empty queries
return results;
}
return results;
}
}