Modelsbuilder modes
Models Builder can be used in different modes:
InMemory models
SourceCode models
The mode is indicated by the Umbraco:CMS:ModelsBuilder:ModelsMode key in the configuration (appsettings.json files).
Corresponds to the InMemoryAuto setting value.
With InMemory models, models are generated and compiled on the fly, in memory, at runtime. They are available in views exclusively.
This is for a setup that exclusively uses the Umbraco backoffice, and do not use custom code such as controllers. Whenever a content type is modified, models are updated without restarting Umbraco (in the same way .cshtml views are recompiled).
Generation can fail for various reasons, in which case Umbraco will run without models (and front-end views fail to render). Umbraco's log file should contain all details about what prevented the generation, but it is probably faster to check the Models Builder dashboard, which should report the last error that was encountered, if any.
Models Builder maintains some files in ~/umbraco/Data/TEMP/InMemoryAuto:
models.generated.cs contains the generated models code
all.generated.cs contains the compiled code (models merged with non-generated files)
models.hash contains a hash code of the content types
all.dll.path contains the path to the compiled DLL file containing all the models
Compiled/generated.cs{GUID}.dll the dll containing all the generated models
models.err contains the last generation error information, if any
The models.hash file is used when Umbraco restarts, to figure out whether models have changed and need to be re-generated. Otherwise, the local models.generated.cs file is reused.
Corresponds to the SourceCodeManual and SourceCodeAuto setting values.
With SourceCode models, models are generated in the ~/umbraco/models directory, and that is all. It is then up to you to decide how to compile the models (e.g. by including them in a Visual Studio solution).
Generation can fail for various reasons, in which case no models are generated. Umbraco's log file should contain all details about what prevented the generation, but it is probably faster to check the Models Builder dashboard, which should report the last error that was encountered, if any.
The modelsbuilder works much in the same way whether using SourceCodeManual or SourceCodeAuto. The only real difference between the two are that with SourceCodeManual you must manually trigger the generation of the models from the models builder dashboard, whereas with SourceCodeAuto the models are automatically generated whenever content types change.
These modes are not available in the embedded version of Models Builder. See the full version of ModelsBuilder.