/// <summary>
/// Process an individual request.
/// </summary>
/// <param name="httpContext">The HTTP context for the current request.</param>
/// <returns>A task that represents the asynchronous operation.</returns>
public virtual async Task Invoke(HttpContext httpContext)
{
if (httpContext == null)
{
throw new ArgumentNullException(nameof(httpContext));
}
try
{
// Because CallContext is cloned at each async operation we cannot
// lazily create the error object when an error is encountered, otherwise
// it will not be available to code outside of the current async context.
// We create it ahead of time so that any cloning just clones the reference
// to the object that will hold any errors.
_localDiagnostic.Value = new DiagnosticHolder();
await _next(httpContext);
}
catch (Exception exception)
{
try
{
if (ShouldDisplayErrorPage(exception))
{
var contextType = _localDiagnostic.Value.ContextType;
var context = (DbContext)httpContext.RequestServices.GetService(contextType);
if (context == null)
{
_logger.LogError(Strings.FormatDatabaseErrorPageMiddleware_ContextNotRegistered(contextType.FullName));
}
else
{
var relationalDatabaseCreator = context.GetService <IDatabaseCreator>() as IRelationalDatabaseCreator;
if (relationalDatabaseCreator == null)
{
_logger.LogDebug(Strings.DatabaseErrorPage_NotRelationalDatabase);
}
else
{
var databaseExists = await relationalDatabaseCreator.ExistsAsync();
var migrationsAssembly = context.GetService <IMigrationsAssembly>();
var modelDiffer = context.GetService <IMigrationsModelDiffer>();
// HasDifferences will return true if there is no model snapshot, but if there is an existing database
// and no model snapshot then we don't want to show the error page since they are most likely targeting
// and existing database and have just misconfigured their model
var pendingModelChanges
= (!databaseExists || migrationsAssembly.ModelSnapshot != null) &&
modelDiffer.HasDifferences(migrationsAssembly.ModelSnapshot?.Model, context.Model);
var pendingMigrations
= (databaseExists
? await context.Database.GetPendingMigrationsAsync()
: context.Database.GetMigrations())
.ToArray();
if (pendingModelChanges || pendingMigrations.Any())
{
var page = new DatabaseErrorPage
{
Model = new DatabaseErrorPageModel(
contextType, exception, databaseExists, pendingModelChanges, pendingMigrations, _options)
};
await page.ExecuteAsync(httpContext);
return;
}
}
}
}
}
catch (Exception e)
{
_logger.LogError(
eventId: 0,
exception: e,
message: Strings.DatabaseErrorPageMiddleware_Exception);
}
throw;
}
}
