Add -e option to dotnet run

src/Cli/dotnet/CommonOptions.cs

@@ -4,6 +4,7 @@
 using System.CommandLine;
 using System.CommandLine.Completions;
 using System.CommandLine.Parsing;
+using System.ComponentModel.DataAnnotations;
 using Microsoft.DotNet.Cli.Utils;
 using Microsoft.DotNet.Tools;
 using Microsoft.DotNet.Tools.Common;
@@ -186,15 +187,23 @@ internal static string ArchOptionValue(ParseResult parseResult) =>
 
         private static IReadOnlyDictionary<string, string> ParseEnvironmentVariables(ArgumentResult argumentResult)
         {
-            Dictionary<string, string> result = [];
+            var result = new Dictionary<string, string>(
+                RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? StringComparer.OrdinalIgnoreCase : StringComparer.Ordinal);
+
             List<CliToken>? invalid = null;
 
             foreach (var token in argumentResult.Tokens)
             {
-                if (token.Value.IndexOf('=') is var index and > 0 &&
-                    token.Value[0..index].Trim() is var name and not "")
+                var separator = token.Value.IndexOf('=');
+                var (name, value) = (separator >= 0)
+                    ? (token.Value[0..separator], token.Value[(separator + 1)..])
+                    : (token.Value, "");
+
+                name = name.Trim();
+
+                if (name != "")
                 {
-                    result[name] = token.Value[(index + 1)..];
+                    result[name] = value;
                 }
                 else
                 {

test/dotnet.Tests/ParserTests/CommonOptionsTests.cs

@@ -24,6 +24,33 @@ public void Duplicates()
         result.Errors.Should().BeEmpty();
     }
 
+    [Fact]
+    public void Duplicates_CasingDifference()
+    {
+        var command = new CliRootCommand();
+        command.Options.Add(CommonOptions.EnvOption);
+
+        var result = command.Parse(["-e", "A=1", "-e", "a=2"]);
+
+        var expected = new Dictionary<string, string>();
+
+        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+        {
+            expected.Add("A", "2");
+        }
+        else
+        {
+            expected.Add("A", "1");
+            expected.Add("a", "2");
+        }
+
+        result.GetValue(CommonOptions.EnvOption)
+            .Should()
+            .BeEquivalentTo(expected);
+
+        result.Errors.Should().BeEmpty();
+    }
+
     [Fact]
     public void MultiplePerToken()
     {
@@ -44,6 +71,21 @@ public void MultiplePerToken()
         result.Errors.Should().BeEmpty();
     }
 
+    [Fact]
+    public void NoValue()
+    {
+        var command = new CliRootCommand();
+        command.Options.Add(CommonOptions.EnvOption);
+
+        var result = command.Parse(["-e", "A"]);
+
+        result.GetValue(CommonOptions.EnvOption)
+            .Should()
+            .BeEquivalentTo(new Dictionary<string, string> { ["A"] = "" });
+
+        result.Errors.Should().BeEmpty();
+    }
+
     [Fact]
     public void WhitespaceTrimming()
     {
@@ -61,7 +103,6 @@ public void WhitespaceTrimming()
 
     [Theory]
     [InlineData("")]
-    [InlineData("X")]
     [InlineData("=")]
     [InlineData("= X")]
     [InlineData("  \u2002 = X")]
@@ -74,7 +115,7 @@ public void Errors(string token)
 
         result.Errors.Select(e => e.Message).Should().BeEquivalentTo(
         [
-            string.Format(CommonLocalizableStrings.IncorrectlyFormattedEnvironmentVariables, token)
+            string.Format(CommonLocalizableStrings.IncorrectlyFormattedEnvironmentVariables, $"'{token}'")
         ]);
     }
 }