Nullables treated as non-nullable at runtime

[farlee2121]

My model includes a DateTime? property

public class CampaignDesignerRequest
{
     //...
     public DateTime? CampaignStartDate { get; set; }
     //...
}

My view inherits the model

@inherits RazorEngineCore.RazorEngineTemplateBase<Fourstarzz.Accessors.ReportTemplates.Models.DesignedCampaign_RenderModel>

At write time, the intellisense recognizes CampaignStartDate as a nullable and shows an error hint if I try to run date string formatting without specifying .Value

Model.CampaignStartDate.Value.ToShortDateString()

However when I run the code, it gives me the error

Microsoft.CSharp.RuntimeBinder.RuntimeBinderException : 'System.DateTime' does not contain a definition for 'Value'

I've tested the same on other value types, like int and double, and get the same kind of error.

Versions

• RazoreEngineCore 2020.9.1
• .NET framework 4.8.

Any thoughts on potential causes?

[farlee2121]

I think I may have a lead. Trying to use Linq select was causing a

Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type

This can be caused by using Linq on dynamic models. The non-generic template base uses dynamic as the type for the whole page model. https://github.com/adoconnection/RazorEngineCore/blob/master/RazorEngineCore/IRazorEngineTemplate.cs

I'm guessing there is some issue with dynamic typing going on here

[adoconnection]

As I can see your view inherits different model DesignedCampaign_RenderModel whereas you looking at CampaignDesignerRequest

Have a look on this test:

public class TestModel
{
    public DateTime? DateTime { get; set; }

}

public class TestTemplate2 : RazorEngineTemplateBase<TestModel>
{
    public void Initialize(TestModel model)
    {
        this.Model = model;
    }
}

RazorEngine razorEngine = new RazorEngine();
DateTime? dateTime = DateTime.Now;

IRazorEngineCompiledTemplate<TestTemplate2> template = razorEngine.Compile<TestTemplate2>("DateTime: @Model.DateTime.Value.ToString()");

string actual = template.Run(instance => instance.Model = new TestModel()
{
        DateTime = dateTime
});

Assert.AreEqual("DateTime: " + dateTime, actual);

[adoconnection]

Also, I get same error as this if I do caching, see #28

[farlee2121]

Woops, I copied the wrong model statement. CampaignDesignerRequest is actually a property on the other model, but I had been running experiments on a simplified version to make sure the parent object wasn't part of the issue.

I am caching as in issue #28. I'll have to test if the issue also happens with model-specific template caches.

[farlee2121]

Ok. I ran a few tests. Using definitely typed templates as you did above, with model-specific caches, and by casting the cache solves the issue.

It also works to cast types within the template, though that could be a bit dangerous.

Definitely a good gotcha to have documented

[farlee2121]

I'd be happy to contribute documentation if we want to promote it from an issue to the wiki or readme

[adoconnection]

you are welcome to push updates in description and wiki :)

[farlee2121]

I'll try to push some changes this week