Azure Search and Date fields

Question

I'm using 8.2 Update-3 with the Azure Toolkit 1.1, deployed to Web App. I've got a template with a Date field on it, and I took a search class that works with Lucene and Solr like this:

[IndexField("date start")]
public DateTime DateStart { get; set; }

And the query expression:

DateTime time;
// ...
.Where(i => i.DateStart >= time)
.OrderBy(i => i.DateStart);

When I run this with Azure Search I get this exception:

System.NotSupportedException: The constant part of the 'GreaterThanOrEqualNode' was expected to be of type 'System.DateTimeOffset', but was of type 'System.DateTime'.

So I converted my result class property and time variable to DateTimeOffset. Then I got this exception instead:

Sitecore.ContentSearch.Azure.Http.Exceptions.AzureSearchServiceRESTCallException: {"error":{"code":"","message":"Invalid expression: Unsupported function call: search.ismatchscoring. This function is not supported in this API version.\r\nParameter name: $filter"}}

And this one:

System.NotSupportedException: IndexFieldUtcDateTimeOffsetValueConverter cannot convert from System.DateTime. at System.ComponentModel.TypeConverter.GetConvertFromException(Object value) at System.ComponentModel.TypeConverter.ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, Object value) at Sitecore.ContentSearch.Azure.Converters.CloudIndexFieldStorageValueFormatter.ReadFromIndexStorageBase(Object indexValue, String fieldName, Type destinationType)

Am I doing date mapping wrong or is this just a limitation of the Azure Search provider or service?

Edit: found the actual search expression in App Insights:

ERROR Azure Search Error [Index=sitecore_web_index] 
ERROR:Error in the request URI, headers, or body Search expression:&search=language_1:(en)&$filter=not search.ismatchscoring('name__:(__Standard Values)', null, 'full', null) and date_start ge 2017-05-17T04:55:13.340Z and (templatesimplemented__/any(t:t eq '{DFFD8BFE-9C7E-4033-AD70-6C600088A9E6}')) and latestversion_1&queryType=full

Weirdly, the unsupported ismatchscoring is apparently coming from .Where(i => i.Name != Sitecore.Constants.StandardValuesItemName) and not the date.

Answer 1

Regarding the ismatchscoring error, this is the cause - apparently the default settings for Azure Search rely on an old preview version of the Azure Search API:

  <!--  USE ISMATCHSCORING
        Determines if Azure Search provider uses ismatchscoring() function to build complex search expressions. 
        This function is available in version 2015-02-28-Preview of Azure Search API and is not available in version 2016-09-01 or earlier versions. 
        When using Azure Search API version 2016-09-01 or earlier versions, this setting must be changed to false. 
        Changing the value to false will limit the support for complex search queries.

        Default value: true
  -->
  <setting name="ContentSearch.Azure.UseIsMatchScoring" value="true"/>

Changing this to false resolved that exception.