NET core configuration array with Bind

2020, Mar 14 2 mins read

New configuration system of.NET core is really nice, but it does not works very well with arrays, I have a configuration object that has an array of FirewallRules

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        public FirewallRule[] Rules { get; set; }

This rule is simply composed by four simple properties.

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public class FirewallRule
{
    internal FirewallRule()
    {
    }

    public FirewallRule(string name, int udpPort, int tcpPort, string secret)
    {
        Name = name;
        UdpPort = udpPort;
        TcpPort = tcpPort;
        Secret = secret;
    }

    public String Name { get; set; }

    public Int32 UdpPort { get; set; }

    public Int32 TcpPort { get; set; }

    public String Secret { get; set; }
}

Ok, nothing complex, now I’m expecting to being able to write this json configuration file to configure a single rule.

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{
  "Rules" : [
    {
      "Name": "Rdp",
      "UdpPort": 23456,
      "TcpPort": 3389,
      "Secret": "this_is_a_secret"
    }
 ]
}

And being able to configure using standard Bind utilities of.NET configuration extensions.

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            const string testValue = @"
{
  ""Rules"" : [
    {
      ""Name"": ""Rdp"",
      ""UdpPort"": 23456,
      ""TcpPort"": 3389,
      ""Secret"": ""this_is_a_secret""
    }
 ]
}";
            using var ms = new MemoryStream(Encoding.UTF8.GetBytes(testValue));
            IConfiguration configuration = new ConfigurationBuilder()
               .SetBasePath(AppDomain.CurrentDomain.BaseDirectory)
               .AddJsonStream(ms)
               .Build();

            var config = new Configuration();
            configuration.Bind(config);

Now I’m disappointed because the test fails because in Rules array I have only a single null element. It seems that Bind does not work perfectly with arrays or am I doing something wrong.

The solution was quite simple, I created a method inside the Configuration object that will allows binding from a standard.NET Core IConfiguration object

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public void Bind(IConfiguration configuration)
{
    configuration.Bind(this);

    List<FirewallRule> rulesList = new List<FirewallRule>();
    var rules = configuration.GetSection("Rules").GetChildren().ToList();
    foreach (var rule in rules)
    {
        var firewallRule = new FirewallRule();
        rule.Bind(firewallRule);
        rulesList.Add(firewallRule);
    }

    Rules = rulesList.ToArray();
}

As you can see I explicitly get the section Rules, and for each child I explicitly created a FirewallRule and populate properties with standard Bind() method. And everything worked perfectly. I’am a little bit puzzled, because I suspect that I’m doing something wrong because base Bind() method should work out of the box, but at least with this fix all tests are still green.

Gian Maria.

Codewrecks

Tags

NET core configuration array with Bind