使用.NET反射查询Azure表存储

Question

I want to write a function GetAny() that can query and return a row from any table in the Azure Table Storage just by supplying the table name tableName and the entity type T with LINQ. So far what I've tried is as follows:

public T GetAny<T>(TableServiceContext tableStorageServiceContext, 
    string tableName, string partitionKey, string applicationName)
{
    var results = from c in tableStorageServiceContext.CreateQuery<T>(tableName)
        where ((T)c).PartitionKey == partitionKey
        select c;

    var query = results.AsTableServiceQuery();
    return query.Execute().FirstOrDefault();
}

, which does not compile since I'm not allowed to cast c into T like I'm trying to.

I also tried to default to TableServiceEntity , but then I still have to cast the resulting TableServiceEntity into the true entity type after GetAny() has been invoked:

TableServiceEntity GetAny(string tableName, string partitionKey)
{
    var results = from c in _tableStorageServiceContext.CreateQuery<TableServiceEntity>(tableName)
                  where c.PartitionKey == partitionKey 
                  select c;

    var query = results.AsTableServiceQuery();
    return query.Execute().FirstOrDefault();
}

Is there a way of doing this with .NET reflection, or perhaps there are other ways of querying the Azure Table Storage that supports not having to implicitly specify the entity type?

Answer 1

You can use following code to query from any Storage Table:

/// <summary>
/// Returns table entities
/// </summary>
public List<dynamic> GetEntities(string tableName, int takeCount, string filters)
    {

        var table = TableClient.GetTableReference(tableName);

        var tableQuery = !filters.IsEmpty()
                             ? new TableQuery<DynamicTableEntity>().Where(filters).Take(takeCount)
                             : new TableQuery<DynamicTableEntity>().Take(takeCount);

        var tableResult = table.ExecuteQuery(tableQuery);

        List<dynamic> dynamicCollection = tableResult.ToDynamicList();

        return dynamicCollection;
    }

The extension method ToDynamicList basically reads through each entity on the result and maps the property value as dynamic type. Storage Library by default hides the values behind bunch of properties such as .BinaryValue , 'BoolValue'

I wrote a generic Storage Table Browser which you can find on github