如何将 EntityResolver 与 Azure 存储一起使用？

Question

我正在编写以下代码以从 Azure 表中检索所有实体。但是我在传递实体解析器委托方面有点卡住了。我在MSDN 上找不到太多参考资料。

谁能指出，如何在下面的代码中使用EntityResover？

public class ATSHelper<T> where T : ITableEntity, new()
{
    CloudStorageAccount storageAccount;
    public ATSHelper(CloudStorageAccount storageAccount)
    {
        this.storageAccount = storageAccount;
    }
    public async Task<IEnumerable<T>> FetchAllEntities(string tableName)
    {
        List<T> allEntities = new List<T>();
        CloudTable table = storageAccount.CreateCloudTableClient().GetTableReference(tableName);
        TableContinuationToken contToken = new TableContinuationToken();
        TableQuery query = new TableQuery();
        CancellationToken cancelToken = new CancellationToken();            

        do
        {
            var qryResp = await table.ExecuteQuerySegmentedAsync<T>(query, ???? EntityResolver ???? ,contToken, cancelToken);
            contToken = qryResp.ContinuationToken;
            allEntities.AddRange(qryResp.Results);
        }
        while (contToken != null);
        return allEntities;
    }
}

Answer 1

Here is a nice article 深入描述表存储。它还包括 EntityResolver 的几个示例。

理想的情况是拥有一个生成所需结果的通用解析器。然后，您可以将其包含在您的通话中。我将在这里引用所提供文章中的一个示例：

EntityResolver<ShapeEntity> shapeResolver = (pk, rk, ts, props, etag) =>
{
    ShapeEntity resolvedEntity = null;
    string shapeType = props["ShapeType"].StringValue;

    if (shapeType == "Rectangle") { resolvedEntity = new RectangleEntity(); }
    else if (shapeType == "Ellipse") { resolvedEntity = new EllipseEntity(); }
    else if (shapeType == "Line") { resolvedEntity = new LineEntity(); }    
    // Potentially throw here if an unknown shape is detected 

    resolvedEntity.PartitionKey = pk;
    resolvedEntity.RowKey = rk;
    resolvedEntity.Timestamp = ts;
    resolvedEntity.ETag = etag;
    resolvedEntity.ReadEntity(props, null);

    return resolvedEntity;
};

    currentSegment = await drawingTable.ExecuteQuerySegmentedAsync(drawingQuery, shapeResolver, currentSegment != null ? currentSegment.ContinuationToken : null);

阅读全文以更好地了解与解析器的交易。