If Migration is not sent to the database, UseExceptionHandler Middleware will not work. Why?

Question

I added a new property in a entity class. I didn't create migration. After that, I tried to use UseExceptionHandler middleware. It successfully triggered error action method but the view didn't appear. Instead, the default developer exception page was displayed. I wonder why this happened. Later, I added new migration and updated the database. After doing so, the middleware worked as expected.

I tried to use UseExceptionHandler middleware. The view didn't appear.

Answer 1

Enables the Developer Exception Page when ASPNETCORE_ENVIRONMENT is set to Development. This is done automatically by the WebApplication.CreateBuilder method. Calls UseExceptionHandler when the value of ASPNETCORE_ENVIRONMENT is anything other than Development. you can delete "!" or remove the judgment condition.

Here's an example：

1） delete "!"

if (app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Home/Error");
    app.UseHsts();
}

2）remove the judgment condition

app.UseExceptionHandler("/Home/Error");
app.UseHsts();

The result is as follows: