This is more of a “Today-I-Learned” post and not a “full-blown How-To article.” If something is completely wrong, please let me know - thanks!

If you work with SQL Azure you might find this familiar:

Unexpected exception occurred: An exception has been raised that is likely due to a transient failure. Consider enabling transient error resiliency by adding ‘EnableRetryOnFailure’ to the ‘UseSqlServer’ call.

EF Core Resiliency

The above error already shows a very simple attempt to “stabilize” your application. If you are using Entity Framework Core, this could look like this:

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    optionsBuilder
        .UseSqlServer(
            @"Server=(localdb)\mssqllocaldb;Database=EFMiscellanous.ConnectionResiliency;Trusted_Connection=True;ConnectRetryCount=0",
            options => options.EnableRetryOnFailure());
}

The EnableRetryOnFailure-Method has a couple of options, like a retry count or the retry delay.

If you don’t use the UseSqlServer-method to configure your context, there are other ways to enable this behavior: See Microsoft Docs

Microsoft.Data.SqlClient - Retry Provider

If you use the “plain” Microsoft.Data.SqlClient NuGet Package to connect to your database have a look at Retry Logic Providers

A basic implementation would look like this:

// Define the retry logic parameters
var options = new SqlRetryLogicOption()
{
    // Tries 5 times before throwing an exception
    NumberOfTries = 5,
    // Preferred gap time to delay before retry
    DeltaTime = TimeSpan.FromSeconds(1),
    // Maximum gap time for each delay time before retry
    MaxTimeInterval = TimeSpan.FromSeconds(20)
};

// Create a retry logic provider
SqlRetryLogicBaseProvider provider = SqlConfigurableRetryFactory.CreateExponentialRetryProvider(options);

// Assumes that connection is a valid SqlConnection object 
// Set the retry logic provider on the connection instance
connection.RetryLogicProvider = provider;
// Establishing the connection will retry if a transient failure occurs.
connection.Open();

You can set a RetryLogicProvider on a Connection and on a SqlCommand.

Some more links and tips

These two options seem to be the “low-level-entry-points”. Of course could you wrap each action with a library like Polly.

During my research I found a good overview: Implementing Resilient Applications.

Hope this helps!