https://dotnetfiddle.net/NI8H1n
I have been having an issue with a DateTime? in a razor template in a netcoreapp3.1. The template is being run through:
Engine.Razor.RunCompile("templateName", "templateKey" model: model);
The model being passed consists of the property:
public DateTime? IssueDate { get; set; }
The razor line that is throwing a null ref error inside the template is:
<td>Issue date: @(result.IssueDate.HasValue ? result.IssueDate.Value.ToString("dd/MM/yyyy") : "")</td>
The error:
Microsoft.CSharp.RuntimeBinder.RuntimeBinderException: Cannot perform runtime binding on a null reference
So after some debugging, I found that if I change the problematic line in the template to:
<td>Issue date: @(result.IssueDate != null? result.IssueDate.ToString("dd/MM/yyyy") : "")</td>
Then we are good to go.
So the question I have is why doesn't the initial line work?
Since your view - copied here below from your Fiddle - does not contain a @model declaration, the type dynamic is being used for the viewmodel.
@(Model.SomeDate.HasValue ? Model.SomeDate.Value.ToString("dd/MM/yyyy") : "No Value")
Once compiled, the above statement looks like below - notice the use of dynamic.
public override async Task ExecuteAsync()
{
this.Write((((dynamic)base.Model).SomeDate.HasValue)
? ((dynamic)base.Model).SomeDate.Value.ToString("dd/MM/yyyy")
: "No Value"
);
}
Consider the information from the documentation about dynamic
- Variables of type dynamic are compiled into variables of type object. Therefore, type dynamic exists only at compile time, not at run time.
- any non-null expression can be converted to the dynamic type
This makes that the type dynamic must evaluate its operations and data types at runtime.
public class SampleViewModel
{
public DateTime? SomeDate {get;set;}
}
Given your model here above, where SomeDate is of type Nullable<DateTime>.
When that SomeDate property would have a value null, you get the Cannot perform runtime binding on a null reference exception, since the code tries to access .HasValue on a null, instead on something that could have been converted to a dynamic (bullet point 2).
When that SomeDate would have a DateTime.Now value as shown in your Fiddle, the dynamic runtime binding concludes that SomeDate must be of type System.DateTime because DateTime.Now is not nullable and only a non-null expression can be converted to the dynamic type (bullet point 2).
Therefore you get the 'System.DateTime' does not contain a definition for 'HasValue' exception, since a DateTime does not contain a HasValue property.
One way to make the HasValue check work, is by including the model declaration in the view, as it avoids having to use the type dynamic - see updated Fiddle.
@model HelloWorldMvcApp.SampleViewModel
@(Model.SomeDate.HasValue ? Model.SomeDate.Value.ToString("dd/MM/yyyy") : "No Value")