Query for documents (.NET)
- DocumentDB supports rich queries against JSON documents stored in each collection.
With a LINQ query
IQueryable<Family> familyQuery = this.client.CreateDocumentQuery<Family>(
UriFactory.CreateDocumentCollectionUri(databaseName, collectionName), queryOptions)
.Where(f => f.LastName == "Andersen");
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With a SQL query
IQueryable<Family> familyQueryInSql = this.client.CreateDocumentQuery<Family>(
UriFactory.CreateDocumentCollectionUri(databaseName, collectionName),
"SELECT * FROM Family WHERE Family.lastName = 'Andersen'",
queryOptions);
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Pagination on a LINQ query
- The FeedOptions is used to set the RequestContinuation property obtained on the first query:
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));
}
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- You can always call once and return the Continuation Token to the client, so the paginated request is sent when the client wants the next page. Using a helper class and an extension:
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;
}
}