Add a built-in EnvironmentBoundary component for Blazor

src/Components/Components/src/EnvironmentComponent.cs

@@ -0,0 +1,136 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.AspNetCore.Components.Rendering;
+using Microsoft.Extensions.Hosting;
+
+namespace Microsoft.AspNetCore.Components;
+
+/// <summary>
+/// A component that renders its child content only when the current hosting environment
+/// matches one of the specified environment names.
+/// </summary>
+/// <remarks>
+/// <para>
+/// This component is similar to the environment tag helper in MVC and Razor Pages.
+/// </para>
+/// <example>
+/// The following example shows how to conditionally render content based on the environment:
+/// <code>
+/// &lt;Environment Include="Development"&gt;
+///     &lt;div class="alert alert-warning"&gt;
+///         You are running in Development mode. Debug features are enabled.
+///     &lt;/div&gt;
+/// &lt;/Environment&gt;
+///
+/// &lt;Environment Include="Development, Staging"&gt;
+///     &lt;p&gt;This is a pre-production environment.&lt;/p&gt;
+/// &lt;/Environment&gt;
+///
+/// &lt;Environment Exclude="Production"&gt;
+///     &lt;p&gt;Debug information: @DateTime.Now&lt;/p&gt;
+/// &lt;/Environment&gt;
+/// </code>
+/// </example>
+/// </remarks>
+public sealed class Environment : ComponentBase
+{
+    private static readonly char[] NameSeparator = [','];
+
+    [Inject]
+    private IHostEnvironment HostEnvironment { get; set; } = default!;
+
+    /// <summary>
+    /// Gets or sets a comma-separated list of environment names in which the content should be rendered.
+    /// If the current environment is also in the <see cref="Exclude"/> list, the content will not be rendered.
+    /// </summary>
+    /// <remarks>
+    /// The specified environment names are compared case insensitively.
+    /// </remarks>
+    [Parameter]
+    public string? Include { get; set; }
+
+    /// <summary>
+    /// Gets or sets a comma-separated list of environment names in which the content will not be rendered.
+    /// </summary>
+    /// <remarks>
+    /// The specified environment names are compared case insensitively.
+    /// </remarks>
+    [Parameter]
+    public string? Exclude { get; set; }
+
+    /// <summary>
+    /// Gets or sets the content to be rendered when the environment matches.
+    /// </summary>
+    [Parameter]
+    public RenderFragment? ChildContent { get; set; }
+
+    /// <inheritdoc />
+    protected override void BuildRenderTree(RenderTreeBuilder builder)
+    {
+        if (ShouldRenderContent())
+        {
+            builder.AddContent(0, ChildContent);
+        }
+    }
+
+    private bool ShouldRenderContent()
+    {
+        var currentEnvironmentName = HostEnvironment.EnvironmentName?.Trim();
+
+        if (string.IsNullOrEmpty(currentEnvironmentName))
+        {
+            return false;
+        }
+
+        // Check exclusions first - if current environment is excluded, don't render
+        if (!string.IsNullOrWhiteSpace(Exclude))
+        {
+            foreach (var environment in ParseEnvironmentNames(Exclude))
+            {
+                if (environment.Equals(currentEnvironmentName, StringComparison.OrdinalIgnoreCase))
+                {
+                    return false;
+                }
+            }
+        }
+
+        // If no inclusions specified, render (unless excluded above)
+        if (string.IsNullOrWhiteSpace(Include))
+        {
+            return true;
+        }
+
+        // Check if current environment is in the include list
+        var hasEnvironments = false;
+        foreach (var environment in ParseEnvironmentNames(Include))
+        {
+            hasEnvironments = true;
+            if (environment.Equals(currentEnvironmentName, StringComparison.OrdinalIgnoreCase))
+            {
+                return true;
+            }
+        }
+
+        // If Include was specified but contained no valid environments, render content
+        // (same behavior as when Include is not specified)
+        if (!hasEnvironments)
+        {
+            return true;
+        }
+
+        return false;
+    }
+
+    private static IEnumerable<string> ParseEnvironmentNames(string names)
+    {
+        foreach (var segment in names.Split(NameSeparator, StringSplitOptions.RemoveEmptyEntries))
+        {
+            var trimmed = segment.Trim();
+            if (trimmed.Length > 0)
+            {
+                yield return trimmed;
+            }
+        }
+    }
+}

src/Components/Components/src/Microsoft.AspNetCore.Components.csproj

@@ -31,6 +31,7 @@
   <Import Project="Microsoft.AspNetCore.Components.Routing.targets" />
 
   <ItemGroup>
+    <Reference Include="Microsoft.Extensions.Hosting.Abstractions" />
     <Reference Include="Microsoft.Extensions.Logging.Abstractions" />
     <Reference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
   </ItemGroup>

src/Components/Components/src/PublicAPI.Unshipped.txt

@@ -1 +1,9 @@
 #nullable enable
+Microsoft.AspNetCore.Components.Environment
+Microsoft.AspNetCore.Components.Environment.ChildContent.get -> Microsoft.AspNetCore.Components.RenderFragment?
+Microsoft.AspNetCore.Components.Environment.ChildContent.set -> void
+Microsoft.AspNetCore.Components.Environment.Environment() -> void
+Microsoft.AspNetCore.Components.Environment.Exclude.get -> string?
+Microsoft.AspNetCore.Components.Environment.Exclude.set -> void
+Microsoft.AspNetCore.Components.Environment.Include.get -> string?
+Microsoft.AspNetCore.Components.Environment.Include.set -> void

src/Components/Components/src/Reflection/ComponentProperties.cs

@@ -239,8 +239,8 @@ private static void ThrowForCaptureUnmatchedValuesConflict(Type targetType, stri
     {
         throw new InvalidOperationException(
             $"The property '{parameterName}' on component type '{targetType.FullName}' cannot be set explicitly " +
-            $"when also used to capture unmatched values. Unmatched values:" + Environment.NewLine +
-            string.Join(Environment.NewLine, unmatched.Keys));
+            $"when also used to capture unmatched values. Unmatched values:" + System.Environment.NewLine +
+            string.Join(System.Environment.NewLine, unmatched.Keys));
     }
 
     [DoesNotReturn]
@@ -260,8 +260,8 @@ private static void ThrowForMultipleCaptureUnmatchedValuesParameters([Dynamicall
         throw new InvalidOperationException(
             $"Multiple properties were found on component type '{targetType.FullName}' with " +
             $"'{nameof(ParameterAttribute)}.{nameof(ParameterAttribute.CaptureUnmatchedValues)}'. Only a single property " +
-            $"per type can use '{nameof(ParameterAttribute)}.{nameof(ParameterAttribute.CaptureUnmatchedValues)}'. Properties:" + Environment.NewLine +
-            string.Join(Environment.NewLine, propertyNames));
+            $"per type can use '{nameof(ParameterAttribute)}.{nameof(ParameterAttribute.CaptureUnmatchedValues)}'. Properties:" + System.Environment.NewLine +
+            string.Join(System.Environment.NewLine, propertyNames));
     }
 
     [DoesNotReturn]