diff --git a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/ref/Microsoft.Extensions.Configuration.CommandLine.cs b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/ref/Microsoft.Extensions.Configuration.CommandLine.cs
index 0e629f4f11569..b1d4b8e21e383 100644
--- a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/ref/Microsoft.Extensions.Configuration.CommandLine.cs
+++ b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/ref/Microsoft.Extensions.Configuration.CommandLine.cs
@@ -8,16 +8,16 @@ namespace Microsoft.Extensions.Configuration
 {
     public static partial class CommandLineConfigurationExtensions
     {
-        public static Microsoft.Extensions.Configuration.IConfigurationBuilder AddCommandLine(this Microsoft.Extensions.Configuration.IConfigurationBuilder builder, System.Action<Microsoft.Extensions.Configuration.CommandLine.CommandLineConfigurationSource> configureSource) { throw null; }
+        public static Microsoft.Extensions.Configuration.IConfigurationBuilder AddCommandLine(this Microsoft.Extensions.Configuration.IConfigurationBuilder builder, System.Action<Microsoft.Extensions.Configuration.CommandLine.CommandLineConfigurationSource>? configureSource) { throw null; }
         public static Microsoft.Extensions.Configuration.IConfigurationBuilder AddCommandLine(this Microsoft.Extensions.Configuration.IConfigurationBuilder configurationBuilder, string[] args) { throw null; }
-        public static Microsoft.Extensions.Configuration.IConfigurationBuilder AddCommandLine(this Microsoft.Extensions.Configuration.IConfigurationBuilder configurationBuilder, string[] args, System.Collections.Generic.IDictionary<string, string> switchMappings) { throw null; }
+        public static Microsoft.Extensions.Configuration.IConfigurationBuilder AddCommandLine(this Microsoft.Extensions.Configuration.IConfigurationBuilder configurationBuilder, string[] args, System.Collections.Generic.IDictionary<string, string>? switchMappings) { throw null; }
     }
 }
 namespace Microsoft.Extensions.Configuration.CommandLine
 {
     public partial class CommandLineConfigurationProvider : Microsoft.Extensions.Configuration.ConfigurationProvider
     {
-        public CommandLineConfigurationProvider(System.Collections.Generic.IEnumerable<string> args, System.Collections.Generic.IDictionary<string, string> switchMappings = null) { }
+        public CommandLineConfigurationProvider(System.Collections.Generic.IEnumerable<string> args, System.Collections.Generic.IDictionary<string, string>? switchMappings = null) { }
         protected System.Collections.Generic.IEnumerable<string> Args { get { throw null; } }
         public override void Load() { }
     }
@@ -25,7 +25,7 @@ public partial class CommandLineConfigurationSource : Microsoft.Extensions.Confi
     {
         public CommandLineConfigurationSource() { }
         public System.Collections.Generic.IEnumerable<string> Args { get { throw null; } set { } }
-        public System.Collections.Generic.IDictionary<string, string> SwitchMappings { get { throw null; } set { } }
+        public System.Collections.Generic.IDictionary<string, string>? SwitchMappings { get { throw null; } set { } }
         public Microsoft.Extensions.Configuration.IConfigurationProvider Build(Microsoft.Extensions.Configuration.IConfigurationBuilder builder) { throw null; }
     }
 }
diff --git a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/ref/Microsoft.Extensions.Configuration.CommandLine.csproj b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/ref/Microsoft.Extensions.Configuration.CommandLine.csproj
index e4886f5e0b697..5be8641b37613 100644
--- a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/ref/Microsoft.Extensions.Configuration.CommandLine.csproj
+++ b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/ref/Microsoft.Extensions.Configuration.CommandLine.csproj
@@ -1,10 +1,20 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
+  
   <ItemGroup>
     <Compile Include="Microsoft.Extensions.Configuration.CommandLine.cs" />
     <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Extensions.Configuration\ref\Microsoft.Extensions.Configuration.csproj" />
     <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Extensions.Configuration.Abstractions\ref\Microsoft.Extensions.Configuration.Abstractions.csproj" />
   </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">
+    <ProjectReference Include="$(LibrariesProjectRoot)System.Runtime\ref\System.Runtime.csproj" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp' and '$(TargetFramework)' != '$(NetCoreAppCurrent)'">
+    <Reference Include="System.Runtime" />
+  </ItemGroup>
 </Project>
diff --git a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationExtensions.cs b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationExtensions.cs
index c5e7ee43326fb..b39998e4d91d7 100644
--- a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationExtensions.cs
+++ b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationExtensions.cs
@@ -152,7 +152,7 @@ public static IConfigurationBuilder AddCommandLine(this IConfigurationBuilder co
         public static IConfigurationBuilder AddCommandLine(
             this IConfigurationBuilder configurationBuilder,
             string[] args,
-            IDictionary<string, string> switchMappings)
+            IDictionary<string, string>? switchMappings)
         {
             configurationBuilder.Add(new CommandLineConfigurationSource { Args = args, SwitchMappings = switchMappings });
             return configurationBuilder;
@@ -164,7 +164,7 @@ public static IConfigurationBuilder AddCommandLine(
         /// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
         /// <param name="configureSource">Configures the source.</param>
         /// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
-        public static IConfigurationBuilder AddCommandLine(this IConfigurationBuilder builder, Action<CommandLineConfigurationSource> configureSource)
+        public static IConfigurationBuilder AddCommandLine(this IConfigurationBuilder builder, Action<CommandLineConfigurationSource>? configureSource)
             => builder.Add(configureSource);
     }
 }
diff --git a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationProvider.cs b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationProvider.cs
index fb1b17a521630..a41d6f541d02f 100644
--- a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationProvider.cs
+++ b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationProvider.cs
@@ -11,14 +11,14 @@ namespace Microsoft.Extensions.Configuration.CommandLine
     /// </summary>
     public class CommandLineConfigurationProvider : ConfigurationProvider
     {
-        private readonly Dictionary<string, string> _switchMappings;
+        private readonly Dictionary<string, string>? _switchMappings;
 
         /// <summary>
         /// Initializes a new instance.
         /// </summary>
         /// <param name="args">The command line args.</param>
         /// <param name="switchMappings">The switch mappings.</param>
-        public CommandLineConfigurationProvider(IEnumerable<string> args, IDictionary<string, string> switchMappings = null)
+        public CommandLineConfigurationProvider(IEnumerable<string> args, IDictionary<string, string>? switchMappings = null)
         {
             Args = args ?? throw new ArgumentNullException(nameof(args));
 
@@ -38,7 +38,7 @@ public CommandLineConfigurationProvider(IEnumerable<string> args, IDictionary<st
         /// </summary>
         public override void Load()
         {
-            var data = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+            var data = new Dictionary<string, string?>(StringComparer.OrdinalIgnoreCase);
             string key, value;
 
             using (IEnumerator<string> enumerator = Args.GetEnumerator())
@@ -68,7 +68,7 @@ public override void Load()
 
                     if (separator < 0)
                     {
-                        // If there is neither equal sign nor prefix in current arugment, it is an invalid format
+                        // If there is neither equal sign nor prefix in current argument, it is an invalid format
                         if (keyStartIndex == 0)
                         {
                             // Ignore invalid formats
@@ -76,7 +76,7 @@ public override void Load()
                         }
 
                         // If the switch is a key in given switch mappings, interpret it
-                        if (_switchMappings != null && _switchMappings.TryGetValue(currentArg, out string mappedKey))
+                        if (_switchMappings != null && _switchMappings.TryGetValue(currentArg, out string? mappedKey))
                         {
                             key = mappedKey;
                         }
@@ -105,7 +105,7 @@ public override void Load()
                         string keySegment = currentArg.Substring(0, separator);
 
                         // If the switch is a key in given switch mappings, interpret it
-                        if (_switchMappings != null && _switchMappings.TryGetValue(keySegment, out string mappedKeySegment))
+                        if (_switchMappings != null && _switchMappings.TryGetValue(keySegment, out string? mappedKeySegment))
                         {
                             key = mappedKeySegment;
                         }
diff --git a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationSource.cs b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationSource.cs
index 36a665e360a48..1dc7ad911811c 100644
--- a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationSource.cs
+++ b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/CommandLineConfigurationSource.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
 using System.Collections.Generic;
 
 namespace Microsoft.Extensions.Configuration.CommandLine
@@ -13,12 +14,12 @@ public class CommandLineConfigurationSource : IConfigurationSource
         /// <summary>
         /// Gets or sets the switch mappings.
         /// </summary>
-        public IDictionary<string, string> SwitchMappings { get; set; }
+        public IDictionary<string, string>? SwitchMappings { get; set; }
 
         /// <summary>
         /// Gets or sets the command line args.
         /// </summary>
-        public IEnumerable<string> Args { get; set; }
+        public IEnumerable<string> Args { get; set; } = Array.Empty<string>();
 
         /// <summary>
         /// Builds the <see cref="CommandLineConfigurationProvider"/> for this source.
diff --git a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/Microsoft.Extensions.Configuration.CommandLine.csproj b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/Microsoft.Extensions.Configuration.CommandLine.csproj
index 8a5598960f20e..bf8e1cce4abb2 100644
--- a/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/Microsoft.Extensions.Configuration.CommandLine.csproj
+++ b/src/libraries/Microsoft.Extensions.Configuration.CommandLine/src/Microsoft.Extensions.Configuration.CommandLine.csproj
@@ -1,8 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <Nullable>enable</Nullable>
     <EnableDefaultItems>true</EnableDefaultItems>
+    <!-- Use targeting pack references instead of granular ones in the project file. -->
+    <DisableImplicitAssemblyReferences>false</DisableImplicitAssemblyReferences>
     <PackageDescription>Command line configuration provider implementation for Microsoft.Extensions.Configuration.</PackageDescription>
   </PropertyGroup>