[Account] Use the ArgumentCompleter attribute to replace the dynamic parameters of Get-AzContext. (#19655)

* [Account] removed dynamic parameters of the Get-AzContext.

* [Account] update changelog.

* Update ChangeLog.md

Co-authored-by: Yunchi Wang <[email protected]>

Author: LucasYao93

src/Accounts/Accounts/ChangeLog.md

@@ -23,6 +23,7 @@
 * Upgraded Azure.Core to 1.25.0 and Azure.Identity to 1.6.1
 * Upgraded Microsoft.ApplicationInsights to 2.13.1
 * Changed target framework of AuthenticationAssemblyLoadContext to netcoreapp3.1.
+* Used the ArgumentCompleter attribute to replace the dynamic parameters of `Get-AzContext`. [#18041]
 * Removed built-in environment of Azure Germany
 
 ## Version 2.10.1

src/Accounts/Accounts/Common/ContextNameCompleterAttribute.cs

@@ -0,0 +1,48 @@
+using Microsoft.Azure.Commands.Common.Authentication.Abstractions;
+using Microsoft.Azure.Commands.Common.Authentication.Models;
+using Microsoft.Azure.Commands.ResourceManager.Common;
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Management.Automation;
+using System.Management.Automation.Language;
+using System.Text;
+
+namespace Microsoft.Azure.Commands.Profile.Common
+{
+    /// <summary>
+    /// This attribute will allow the user to autocomplete the values for valid Azure Context names when applied to context name related cmdlet parameters.
+    /// </summary>
+    public class ContextNameCompleterAttribute : ArgumentCompleterAttribute, IArgumentCompleter
+    {
+        /// <summary>
+        /// Initializes a new instance of <see cref="ContextNameCompleterAttribute" /> .
+        /// </summary>
+        public ContextNameCompleterAttribute():base(typeof(ContextNameCompleterAttribute))
+        {
+
+        }
+
+        /// <summary>
+        /// Implementations CompleteArgument function of the <see cref="IArgumentCompleter"/>.
+        /// </summary>
+        public IEnumerable<CompletionResult> CompleteArgument(string commandName, string parameterName, string wordToComplete, CommandAst commandAst, IDictionary fakeBoundParameters)
+        {
+            var profile = AzureRmProfileProvider.Instance.Profile; // Object profile with DefaultContextKey.
+            AzureRmProfile localProfile = profile as AzureRmProfile;
+            if (localProfile.Contexts != null && localProfile.Contexts.Count > 0)
+            {
+                IEnumerable<string> names = localProfile.Contexts.Keys.ToArray();
+                foreach (string name in names)
+                {
+                    yield return new CompletionResult($"'{name}'", $"'{name}'", CompletionResultType.ParameterValue, $"'{name}'");
+                }
+            } 
+            else
+            {   
+                yield return new CompletionResult($"{localProfile.DefaultContextKey}", $"{localProfile.DefaultContextKey}", CompletionResultType.ParameterValue, $"{localProfile.DefaultContextKey}");
+            }
+        }
+    }
+}

src/Accounts/Accounts/Context/GetAzureRMContext.cs

@@ -20,6 +20,7 @@
 using Microsoft.Azure.Commands.Common.Authentication;
 using Microsoft.Azure.Commands.Common.Authentication.Abstractions;
 using Microsoft.Azure.Commands.Common.Authentication.Models;
+using Microsoft.Azure.Commands.Profile.Common;
 using Microsoft.Azure.Commands.Profile.Models.Core;
 using Microsoft.Azure.Commands.ResourceManager.Common;
 using Microsoft.WindowsAzure.Commands.Utilities.Common;
@@ -34,6 +35,11 @@ namespace Microsoft.Azure.Commands.Profile
     public class GetAzureRMContextCommand : AzureRMCmdlet, IDynamicParameters
     {
         public const string ListAllParameterSet = "ListAllContexts", GetSingleParameterSet = "GetSingleContext";
+
+        [Parameter(Position = 0, Mandatory = false, HelpMessage = "The name of the context", ParameterSetName = GetSingleParameterSet)]
+        [ContextNameCompleter]
+        public string Name { get; set; }
+
         /// <summary>
         /// Gets the current default context.
         /// </summary>
@@ -143,25 +149,5 @@ void WriteContext(IAzureContext azureContext, string name)
 
             WriteObject(context);
         }
-
-        public new object GetDynamicParameters()
-        {
-            var parameters = base.GetDynamicParameters() as RuntimeDefinedParameterDictionary;
-            AzureRmProfile localProfile = DefaultProfile as AzureRmProfile;
-            if (localProfile != null && localProfile.Contexts != null && localProfile.Contexts.Count > 0)
-            {
-                var nameParameter = new RuntimeDefinedParameter(
-                "Name", typeof(string),
-                    new Collection<Attribute>()
-                    {
-                        new ParameterAttribute { Position =0, Mandatory=false, HelpMessage="The name of the context", ParameterSetName=GetSingleParameterSet },
-                        new ValidateSetAttribute((DefaultProfile as AzureRmProfile).Contexts.Keys.ToArray())
-                    }
-                );
-                parameters.Add(nameParameter.Name, nameParameter);
-            }
-
-            return parameters;
-        }
     }
 }