查詢文件（.NET）

DocumentDB 支援對儲存在每個集合中的 JSON 文件的豐富查詢。 ****

使用 LINQ 查詢

IQueryable<Family> familyQuery = this.client.CreateDocumentQuery<Family>(
    UriFactory.CreateDocumentCollectionUri(databaseName, collectionName), queryOptions)
    .Where(f => f.LastName == "Andersen");

使用 SQL 查詢

IQueryable<Family> familyQueryInSql = this.client.CreateDocumentQuery<Family>(
    UriFactory.CreateDocumentCollectionUri(databaseName, collectionName),
    "SELECT * FROM Family WHERE Family.lastName = 'Andersen'",
    queryOptions);

LINQ 查詢的分頁

所述 FeedOptions 被用於設定 RequestContinuation 在第一查詢獲得的屬性：

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));
}

你始終可以呼叫一次並將 Continuation Token 返回給客戶端，以便在客戶端需要下一頁時傳送分頁請求。使用幫助程式類和副檔名：

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;
        }
}