TempData support for Blazor

src/Components/Components/src/ITempData.cs

@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.Components;
+
+/// <summary>
+/// Provides a dictionary for storing data that is needed for subsequent requests.
+/// Data stored in TempData is automatically removed after it is read unless
+/// <see cref="Keep()"/> or <see cref="Keep(string)"/> is called, or it is accessed via <see cref="Peek(string)"/>.
+/// </summary>
+public interface ITempData : IDictionary<string, object?>
+{
+    /// <summary>
+    /// Gets the value associated with the specified key and then schedules it for deletion.
+    /// </summary>
+    object? Get(string key);
+
+    /// <summary>
+    /// Gets the value associated with the specified key without scheduling it for deletion.
+    /// </summary>
+    object? Peek(string key);
+
+    /// <summary>
+    /// Makes all of the keys currently in TempData persist for another request.
+    /// </summary>
+    void Keep();
+
+    /// <summary>
+    /// Makes the element with the <paramref name="key"/> persist for another request.
+    /// </summary>
+    void Keep(string key);
+}

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

@@ -1,4 +1,22 @@
 #nullable enable
+Microsoft.AspNetCore.Components.ITempData
+Microsoft.AspNetCore.Components.ITempData.Get(string! key) -> object?
+Microsoft.AspNetCore.Components.ITempData.Keep() -> void
+Microsoft.AspNetCore.Components.ITempData.Keep(string! key) -> void
+Microsoft.AspNetCore.Components.ITempData.Peek(string! key) -> object?
+Microsoft.AspNetCore.Components.TempData
+Microsoft.AspNetCore.Components.TempData.TempData() -> void
+Microsoft.AspNetCore.Components.TempData.Get(string! key) -> object?
+Microsoft.AspNetCore.Components.TempData.this[string! key].get -> object?
+Microsoft.AspNetCore.Components.TempData.this[string! key].set -> void
+Microsoft.AspNetCore.Components.TempData.Keep() -> void
+Microsoft.AspNetCore.Components.TempData.Keep(string! key) -> void
+Microsoft.AspNetCore.Components.TempData.Peek(string! key) -> object?
+Microsoft.AspNetCore.Components.TempData.Clear() -> void
+Microsoft.AspNetCore.Components.TempData.Remove(string! key) -> bool
+Microsoft.AspNetCore.Components.TempData.ContainsKey(string! key) -> bool
+Microsoft.AspNetCore.Components.TempData.Load(System.Collections.Generic.IDictionary<string!, object?>! data) -> void
+Microsoft.AspNetCore.Components.TempData.Save() -> System.Collections.Generic.IDictionary<string!, object?>!
 *REMOVED*Microsoft.AspNetCore.Components.ResourceAsset.ResourceAsset(string! url, System.Collections.Generic.IReadOnlyList<Microsoft.AspNetCore.Components.ResourceAssetProperty!>? properties) -> void
 *REMOVED*Microsoft.AspNetCore.Components.Routing.Router.PreferExactMatches.get -> bool
 *REMOVED*Microsoft.AspNetCore.Components.Routing.Router.PreferExactMatches.set -> void

src/Components/Components/src/TempData.cs

@@ -0,0 +1,184 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections;
+
+namespace Microsoft.AspNetCore.Components;
+
+/// <inheritdoc/>
+public class TempData : ITempData
+{
+    private readonly Dictionary<string, object?> _data = new(StringComparer.OrdinalIgnoreCase);
+    private readonly HashSet<string> _retainedKeys = new(StringComparer.OrdinalIgnoreCase);
+
+    /// <inheritdoc/>
+    public object? this[string key]
+    {
+        get => Get(key);
+        set
+        {
+            _data[key] = value;
+            _retainedKeys.Add(key);
+        }
+    }
+
+    /// <inheritdoc/>
+    public object? Get(string key)
+    {
+        _retainedKeys.Remove(key);
+        return _data.GetValueOrDefault(key);
+    }
+
+    /// <inheritdoc/>
+    public object? Peek(string key)
+    {
+        return _data.GetValueOrDefault(key);
+    }
+
+    /// <inheritdoc/>
+    public void Keep()
+    {
+        _retainedKeys.Clear();
+        _retainedKeys.UnionWith(_data.Keys);
+    }
+
+    /// <inheritdoc/>
+    public void Keep(string key)
+    {
+        if (_data.ContainsKey(key))
+        {
+            _retainedKeys.Add(key);
+        }
+    }
+
+    /// <inheritdoc/>
+    public bool ContainsKey(string key)
+    {
+        return _data.ContainsKey(key);
+    }
+
+    /// <inheritdoc/>
+    public bool Remove(string key)
+    {
+        _retainedKeys.Remove(key);
+        return _data.Remove(key);
+    }
+
+    /// <summary>
+    /// Gets the data that should be saved for the next request.
+    /// </summary>
+    public IDictionary<string, object?> Save()
+    {
+        var dataToSave = new Dictionary<string, object?>();
+        foreach (var key in _retainedKeys)
+        {
+            dataToSave[key] = _data[key];
+        }
+        return dataToSave;
+    }
+
+    /// <summary>
+    /// Loads data from a <paramref name="data"/> into the TempData dictionary.
+    /// </summary>
+    public void Load(IDictionary<string, object?> data)
+    {
+        _data.Clear();
+        _retainedKeys.Clear();
+        foreach (var kvp in data)
+        {
+            _data[kvp.Key] = kvp.Value;
+            _retainedKeys.Add(kvp.Key);
+        }
+    }
+
+    /// <inheritdoc/>
+    public void Clear()
+    {
+        _data.Clear();
+        _retainedKeys.Clear();
+    }
+
+    ICollection<string> IDictionary<string, object?>.Keys => _data.Keys;
+
+    ICollection<object?> IDictionary<string, object?>.Values => _data.Values;
+
+    int ICollection<KeyValuePair<string, object?>>.Count => _data.Count;
+
+    bool ICollection<KeyValuePair<string, object?>>.IsReadOnly => ((ICollection<KeyValuePair<string, object?>>)_data).IsReadOnly;
+
+    void IDictionary<string, object?>.Add(string key, object? value)
+    {
+        _data.Add(key, value);
+        _retainedKeys.Add(key);
+    }
+
+    bool IDictionary<string, object?>.TryGetValue(string key, out object? value)
+    {
+        _retainedKeys.Remove(key);
+        return _data.TryGetValue(key, out value);
+    }
+
+    void ICollection<KeyValuePair<string, object?>>.Add(KeyValuePair<string, object?> item)
+    {
+        ((IDictionary<string, object?>)this).Add(item.Key, item.Value);
+    }
+
+    bool ICollection<KeyValuePair<string, object?>>.Contains(KeyValuePair<string, object?> item)
+    {
+        return ContainsKey(item.Key) && _data[item.Key] == item.Value;
+    }
+
+    void ICollection<KeyValuePair<string, object?>>.CopyTo(KeyValuePair<string, object?>[] array, int arrayIndex)
+    {
+        ((ICollection<KeyValuePair<string, object?>>)_data).CopyTo(array, arrayIndex);
+    }
+
+    bool ICollection<KeyValuePair<string, object?>>.Remove(KeyValuePair<string, object?> item)
+    {
+        if (((ICollection<KeyValuePair<string, object?>>)_data).Remove(item))
+        {
+            _retainedKeys.Remove(item.Key);
+            return true;
+        }
+        return false;
+    }
+
+    IEnumerator<KeyValuePair<string, object?>> IEnumerable<KeyValuePair<string, object?>>.GetEnumerator()
+    {
+        return new TempDataEnumerator(this);
+    }
+
+    IEnumerator IEnumerable.GetEnumerator()
+    {
+        return new TempDataEnumerator(this);
+    }
+
+    class TempDataEnumerator : IEnumerator<KeyValuePair<string, object?>>
+    {
+        private readonly IEnumerator<KeyValuePair<string, object?>> _innerEnumerator;
+
+        public TempDataEnumerator(TempData tempData)
+        {
+            _innerEnumerator = tempData._data.GetEnumerator();
+        }
+
+        public KeyValuePair<string, object?> Current => _innerEnumerator.Current;
+
+        object IEnumerator.Current => _innerEnumerator.Current;
+
+        public void Dispose()
+        {
+            _innerEnumerator.Dispose();
+        }
+
+        public bool MoveNext()
+        {
+            return _innerEnumerator.MoveNext();
+        }
+
+        public void Reset()
+        {
+            _innerEnumerator.Reset();
+        }
+    }
+}

src/Components/Endpoints/src/DependencyInjection/RazorComponentsServiceCollectionExtensions.cs

@@ -74,6 +74,26 @@ public static IRazorComponentsBuilder AddRazorComponents(this IServiceCollection
         services.TryAddCascadingValue(sp => sp.GetRequiredService<EndpointHtmlRenderer>().HttpContext);
         services.TryAddScoped<WebAssemblySettingsEmitter>();
         services.TryAddScoped<ResourcePreloadService>();
+        services.TryAddCascadingValue(sp =>
+        {
+            var httpContext = sp.GetRequiredService<EndpointHtmlRenderer>().HttpContext;
+            if (httpContext is null)
+            {
+                return null!;
+            }
+            var key = typeof(ITempData);
+            if (!httpContext.Items.TryGetValue(key, out var tempData))
+            {
+                var tempDataInstance = TempDataService.Load(httpContext);
+                httpContext.Items[key] = tempDataInstance;
+                httpContext.Response.OnStarting(() =>
+                {
+                    TempDataService.Save(httpContext, tempDataInstance);
+                    return Task.CompletedTask;
+                });
+            }
+            return (ITempData)httpContext.Items[key]!;
+        });
 
         services.TryAddScoped<ResourceCollectionProvider>();
         RegisterPersistentComponentStateServiceCollectionExtensions.AddPersistentServiceRegistration<ResourceCollectionProvider>(services, RenderMode.InteractiveWebAssembly);