C# SQLConnection.Open() hangs, with no exception

I am using C# in Visual Studio 2019, with Xamarin.Forms, and SQl in SSMS 2018 and have the below code (where [] is used to replace unneccessary information)

try
{
  using(SqlConnection connection = new SqlConnection())
  {
     connection.ConnectionString = "Server=[ServerName]; Database=[DatabaseName]; User Id= [UserID]; Password=[Password]";

     connection.Open();

     SqlCommand command = new SqlCommand("SELECT * from [TableName]", connection);

     [Does stuff here]
  }
}
catch (Exception ex)
{
  System.Diagnostics.Debug.WriteLine(ex)
}

When I run this, it hangs indefinitely at connection.Open(). Debug mode continues to run and appears to move on from Connection.Open(), but never reaches the next line.

I have attempted this with different versions of the ConnectionString, using different databases and with Trusted_Connection=true instead of specifiying the username and password but they have made no difference. Adding Connection Timeout = 5 to the connectionString has no effect.

I believe it is probably an issue with my settings in SQL but as I am a novice with this I have no idea where to start and the similar forums posts I have checked have been given answers along the lines of Connection Timeout (Connection.open for hangs indefinitely, no exception is thrown) or never got answered.

Any advice would be greatly appreciated.

Answer

Can you log into SSMS with the credentials that are in the connection string?

Otherwise I’ve had luck making sure the connection isn’t already open or broken first:

if (connection.State == ConnectionState.Closed || connection.State == ConnectionState.Broken)
{
    connection.Open();
}