GetOrNullAsync

Author: sergey-shandar

experiments/Azure.Experiments/Azure.Experiments/Compute/VirtualMachineParameters.cs

@@ -18,7 +18,7 @@ public VirtualMachineParameters(
             Ni = ni;
         }
 
-        public override Task<VirtualMachine> GetAsync(GetContext context)
+        protected override Task<VirtualMachine> GetAsync(GetContext context)
             => context
                 .Context
                 .CreateCompute()

experiments/Azure.Experiments/Azure.Experiments/GetContext.cs

@@ -1,4 +1,5 @@
-using System.Collections.Concurrent;
+using System;
+using System.Collections.Concurrent;
 using System.Threading.Tasks;
 
 namespace Microsoft.Azure.Experiments
@@ -12,25 +13,13 @@ public GetContext(Context context)
             Context = context;
         }
 
-        public async Task<T> GetOrNullAsync<T>(Parameters<T> parameters)
+        public async Task<T> GetOrAdd<T>(Parameters<T> parameters, Func<Task<T>> get)
+            where T : class
         {
-            var result = await Map.GetOrAdd(
-                parameters, _ => GetObjectOrNullAsync(parameters));
+            var result = await Map.GetOrAdd(parameters, async _ => await get());
             return (T)result;
         }
 
-        private async Task<object> GetObjectOrNullAsync<T>(Parameters<T> parameters)
-        {
-            try
-            {
-                return await parameters.GetAsync(this); 
-            }
-            catch
-            {
-                return null;
-            }
-        }
-
         private ConcurrentDictionary<Parameters, Task<object>> Map { get; }
             = new ConcurrentDictionary<Parameters, Task<object>>();
     }

experiments/Azure.Experiments/Azure.Experiments/Network/NetworkInterfaceParameters.cs

@@ -27,7 +27,7 @@ public NetworkInterfaceParameters(
             Pia = pia;
         }
 
-        public override Task<NetworkInterface> GetAsync(GetContext context)
+        protected override Task<NetworkInterface> GetAsync(GetContext context)
             => context
                 .Context
                 .CreateNetwork()

experiments/Azure.Experiments/Azure.Experiments/Network/NetworkSecurityGroupParameters.cs

@@ -13,7 +13,7 @@ public NetworkSecurityGroupParameters(
         {
         }
 
-        public override Task<NetworkSecurityGroup> GetAsync(GetContext context)
+        protected override Task<NetworkSecurityGroup> GetAsync(GetContext context)
             => context
                 .Context
                 .CreateNetwork()

experiments/Azure.Experiments/Azure.Experiments/Network/PublicIpAddressParameters.cs

@@ -14,7 +14,7 @@ public PublicIpAddressParameters(
         {
         }
 
-        public override Task<PublicIPAddress> GetAsync(GetContext context)
+        protected override Task<PublicIPAddress> GetAsync(GetContext context)
             => context
                 .Context
                 .CreateNetwork()

experiments/Azure.Experiments/Azure.Experiments/Network/SubnetParameters.cs

@@ -15,9 +15,9 @@ public SubnetParameters(
             VirtualNetwork = virtualNetwork;
         }
 
-        public override async Task<Subnet> GetAsync(GetContext context)
+        protected override async Task<Subnet> GetAsync(GetContext context)
         {
-            var virtualNetwork = await context.GetOrNullAsync(VirtualNetwork);
+            var virtualNetwork = await VirtualNetwork.GetOrNullAsync(context);
             return virtualNetwork?.Subnets.FirstOrDefault(s => s.Name == Name);
         }
     }

experiments/Azure.Experiments/Azure.Experiments/Network/VirtualNetworkParameters.cs

@@ -13,7 +13,7 @@ public VirtualNetworkParameters(
         {
         }
 
-        public override Task<VirtualNetwork> GetAsync(GetContext context)
+        protected override Task<VirtualNetwork> GetAsync(GetContext context)
             => context
                 .Context
                 .CreateNetwork()

experiments/Azure.Experiments/Azure.Experiments/Parameters.cs

@@ -1,5 +1,7 @@
-using System.Collections.Generic;
+using Microsoft.Rest.Azure;
+using System.Collections.Generic;
 using System.Linq;
+using System.Net;
 using System.Threading.Tasks;
 
 namespace Microsoft.Azure.Experiments
@@ -21,12 +23,29 @@ protected Parameters(string name, IEnumerable<Parameters> dependencies)
     }
 
     public abstract class Parameters<T> : Parameters
+        where T : class
     {
-        protected Parameters(string name, IEnumerable<Parameters> parameters) 
+        protected Parameters(string name, IEnumerable<Parameters> parameters)
             : base(name, parameters)
         {
         }
 
-        public abstract Task<T> GetAsync(GetContext context);
+        public async Task<T> GetOrNullAsync(GetContext context)
+            => await context.GetOrAdd(
+                this, 
+                async () => 
+                {
+                    try
+                    {
+                        return await GetAsync(context);
+                    }
+                    catch (CloudException e)
+                        when (e.Response.StatusCode == HttpStatusCode.NotFound)
+                    {
+                        return null;
+                    }
+                });
+
+        protected abstract Task<T> GetAsync(GetContext context);
     }
 }

experiments/Azure.Experiments/Azure.Experiments/ResourceParameters.cs

@@ -4,6 +4,7 @@
 namespace Microsoft.Azure.Experiments
 {
     public abstract class ResourceParameters<T> : Parameters<T>
+        where T : class
     {
         public ResourceGroupParameters ResourceGroup { get; }