Question

I am trying to create an id for an input by doing the following

    id="@ViewData.ModelMetadata.ContainerType.Name + "_" +  @ViewData.TemplateInfo.GetFullHtmlFieldId("FromDate")"

but it is coming through with id=”propertyName +”. How can I concatenate the two together with an underscore in the middle in a razor view?

Answer 1

You can use the @(expression) syntax to express an explicit code expression.

You need to be explicit here because the space after @ViewData.ModelMetadata.ContainerType.Name is not a valid character for a C# identifier so the evalutation stops there.

The algorithm used by Razor for processing implicit code expression is the following:

1. Parse an identifier – As soon as we see a character that isn’t valid in a C# or VB identifier, we stop and move to step 2
2. Check for brackets – If we see “(” or “[“, go to step 2.1., otherwise, go to step 3
   1. Parse until the matching “)” or “]” (we track nested “()” and “[]” pairs and ignore “()[]” we see in strings or comments)
   2. Go back to step 2
3. Check for a “.” – If we see one, go to step 3.1, otherwise, DO NOT ACCEPT THE “.” as code, and go to step 4
   1. If the character AFTER the “.” is a valid identifier, accept the “.” and go back to step 1, otherwise, go to step 4
4. Done!

(Taken from ScottGu’s Blog)