aspnetcore/src/Microsoft.AspNet.Mvc.Razor/RazorPage.cs

953 lines
38 KiB
C#

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Security.Claims;
using System.Threading.Tasks;
using Microsoft.AspNet.Antiforgery;
using Microsoft.AspNet.Html.Abstractions;
using Microsoft.AspNet.Http;
using Microsoft.AspNet.Mvc.Actions;
using Microsoft.AspNet.Mvc.Razor.Internal;
using Microsoft.AspNet.Mvc.Rendering;
using Microsoft.AspNet.Mvc.ViewFeatures;
using Microsoft.AspNet.PageExecutionInstrumentation;
using Microsoft.AspNet.Razor.Runtime.TagHelpers;
using Microsoft.Framework.DependencyInjection;
using Microsoft.Framework.Internal;
using Microsoft.Framework.WebEncoders;
namespace Microsoft.AspNet.Mvc.Razor
{
/// <summary>
/// Represents properties and methods that are needed in order to render a view that uses Razor syntax.
/// </summary>
public abstract class RazorPage : IRazorPage
{
private readonly HashSet<string> _renderedSections = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
private readonly Stack<TextWriter> _writerScopes;
private TextWriter _originalWriter;
private IUrlHelper _urlHelper;
private ITagHelperActivator _tagHelperActivator;
private ITypeActivatorCache _typeActivatorCache;
private bool _renderedBody;
public RazorPage()
{
SectionWriters = new Dictionary<string, RenderAsyncDelegate>(StringComparer.OrdinalIgnoreCase);
_writerScopes = new Stack<TextWriter>();
}
public HttpContext Context
{
get
{
if (ViewContext == null)
{
return null;
}
return ViewContext.HttpContext;
}
}
/// <inheritdoc />
public string Path { get; set; }
/// <inheritdoc />
public ViewContext ViewContext { get; set; }
/// <inheritdoc />
public string Layout { get; set; }
/// <inheritdoc />
public bool IsPartial { get; set; }
/// <summary>
/// Gets the <see cref="IHtmlEncoder"/> to be used for encoding HTML.
/// </summary>
[RazorInject]
public IHtmlEncoder HtmlEncoder { get; set; }
/// <inheritdoc />
public IPageExecutionContext PageExecutionContext { get; set; }
/// <summary>
/// Gets the TextWriter that the page is writing output to.
/// </summary>
public virtual TextWriter Output
{
get
{
if (ViewContext == null)
{
var message = Resources.FormatViewContextMustBeSet("ViewContext", "Output");
throw new InvalidOperationException(message);
}
return ViewContext.Writer;
}
}
public virtual ClaimsPrincipal User
{
get
{
if (Context == null)
{
return null;
}
return Context.User;
}
}
public dynamic ViewBag
{
get
{
return ViewContext?.ViewBag;
}
}
/// <summary>
/// Gets the <see cref="ITempDataDictionary"/> from the <see cref="ViewContext"/>.
/// </summary>
/// <remarks>Returns null if <see cref="ViewContext"/> is null.</remarks>
public ITempDataDictionary TempData
{
get
{
return ViewContext?.TempData;
}
}
/// <inheritdoc />
public Func<TextWriter, Task> RenderBodyDelegateAsync { get; set; }
/// <inheritdoc />
public bool IsLayoutBeingRendered { get; set; }
/// <inheritdoc />
public IDictionary<string, RenderAsyncDelegate> PreviousSectionWriters { get; set; }
/// <inheritdoc />
public IDictionary<string, RenderAsyncDelegate> SectionWriters { get; private set; }
/// <inheritdoc />
public abstract Task ExecuteAsync();
private ITagHelperActivator TagHelperActivator
{
get
{
if (_tagHelperActivator == null)
{
var services = ViewContext.HttpContext.RequestServices;
_tagHelperActivator = services.GetRequiredService<ITagHelperActivator>();
}
return _tagHelperActivator;
}
}
private ITypeActivatorCache TypeActivatorCache
{
get
{
if (_typeActivatorCache == null)
{
var services = ViewContext.HttpContext.RequestServices;
_typeActivatorCache = services.GetRequiredService<ITypeActivatorCache>();
}
return _typeActivatorCache;
}
}
/// <summary>
/// Format an error message about using an indexer when the tag helper property is <c>null</c>.
/// </summary>
/// <param name="attributeName">Name of the HTML attribute associated with the indexer.</param>
/// <param name="tagHelperTypeName">Full name of the tag helper <see cref="Type"/>.</param>
/// <param name="propertyName">Dictionary property in the tag helper.</param>
/// <returns>An error message about using an indexer when the tag helper property is <c>null</c>.</returns>
public static string InvalidTagHelperIndexerAssignment(
string attributeName,
string tagHelperTypeName,
string propertyName)
{
return Resources.FormatRazorPage_InvalidTagHelperIndexerAssignment(
attributeName,
tagHelperTypeName,
propertyName);
}
/// <summary>
/// Creates and activates a <see cref="ITagHelper"/>.
/// </summary>
/// <typeparam name="TTagHelper">A <see cref="ITagHelper"/> type.</typeparam>
/// <returns>The activated <see cref="ITagHelper"/>.</returns>
/// <remarks>
/// <typeparamref name="TTagHelper"/> must have a parameterless constructor.
/// </remarks>
public TTagHelper CreateTagHelper<TTagHelper>() where TTagHelper : ITagHelper
{
var tagHelper = TypeActivatorCache.CreateInstance<TTagHelper>(
ViewContext.HttpContext.RequestServices,
typeof(TTagHelper));
TagHelperActivator.Activate(tagHelper, ViewContext);
return tagHelper;
}
/// <summary>
/// Starts a new writing scope.
/// </summary>
/// <remarks>
/// All writes to the <see cref="Output"/> or <see cref="ViewContext.Writer"/> after calling this method will
/// be buffered until <see cref="EndTagHelperWritingScope"/> is called.
/// </remarks>
public void StartTagHelperWritingScope()
{
StartTagHelperWritingScope(new StringCollectionTextWriter(Output.Encoding));
}
/// <summary>
/// Starts a new writing scope with the given <paramref name="writer"/>.
/// </summary>
/// <remarks>
/// All writes to the <see cref="Output"/> or <see cref="ViewContext.Writer"/> after calling this method will
/// be buffered until <see cref="EndTagHelperWritingScope"/> is called.
/// </remarks>
public void StartTagHelperWritingScope([NotNull] TextWriter writer)
{
// If there isn't a base writer take the ViewContext.Writer
if (_originalWriter == null)
{
_originalWriter = ViewContext.Writer;
}
// We need to replace the ViewContext's Writer to ensure that all content (including content written
// from HTML helpers) is redirected.
ViewContext.Writer = writer;
_writerScopes.Push(ViewContext.Writer);
}
/// <summary>
/// Ends the current writing scope that was started by calling <see cref="StartTagHelperWritingScope"/>.
/// </summary>
/// <returns>The <see cref="TextWriter"/> that contains the content written to the <see cref="Output"/> or
/// <see cref="ViewContext.Writer"/> during the writing scope.</returns>
public TagHelperContent EndTagHelperWritingScope()
{
if (_writerScopes.Count == 0)
{
throw new InvalidOperationException(Resources.RazorPage_ThereIsNoActiveWritingScopeToEnd);
}
var writer = _writerScopes.Pop();
if (_writerScopes.Count > 0)
{
ViewContext.Writer = _writerScopes.Peek();
}
else
{
ViewContext.Writer = _originalWriter;
// No longer a base writer
_originalWriter = null;
}
var tagHelperContentWrapperTextWriter = new TagHelperContentWrapperTextWriter(Output.Encoding);
var razorWriter = writer as RazorTextWriter;
if (razorWriter != null)
{
razorWriter.CopyTo(tagHelperContentWrapperTextWriter);
}
else
{
var stringCollectionTextWriter = writer as StringCollectionTextWriter;
if (stringCollectionTextWriter != null)
{
stringCollectionTextWriter.CopyTo(tagHelperContentWrapperTextWriter, HtmlEncoder);
}
else
{
tagHelperContentWrapperTextWriter.Write(writer.ToString());
}
}
return tagHelperContentWrapperTextWriter.Content;
}
/// <summary>
/// Writes the content of a specified <paramref name="tagHelperExecutionContext"/>.
/// </summary>
/// <param name="tagHelperExecutionContext">The execution context containing the content.</param>
/// <returns>
/// A <see cref="Task"/> that on completion writes the <paramref name="tagHelperExecutionContext"/> content.
/// </returns>
public Task WriteTagHelperAsync([NotNull] TagHelperExecutionContext tagHelperExecutionContext)
{
return WriteTagHelperToAsync(Output, tagHelperExecutionContext);
}
/// <summary>
/// Writes the content of a specified <paramref name="tagHelperExecutionContext"/> to the specified
/// <paramref name="writer"/>.
/// </summary>
/// <param name="writer">The <see cref="TextWriter"/> instance to write to.</param>
/// <param name="tagHelperExecutionContext">The execution context containing the content.</param>
/// <returns>
/// A <see cref="Task"/> that on completion writes the <paramref name="tagHelperExecutionContext"/> content
/// to the <paramref name="writer"/>.
/// </returns>
public async Task WriteTagHelperToAsync(
[NotNull] TextWriter writer,
[NotNull] TagHelperExecutionContext tagHelperExecutionContext)
{
var tagHelperOutput = tagHelperExecutionContext.Output;
var isTagNameNullOrWhitespace = string.IsNullOrWhiteSpace(tagHelperOutput.TagName);
WriteTo(writer, tagHelperOutput.PreElement);
if (!isTagNameNullOrWhitespace)
{
writer.Write('<');
writer.Write(tagHelperOutput.TagName);
foreach (var attribute in tagHelperOutput.Attributes)
{
writer.Write(' ');
writer.Write(attribute.Name);
if (!attribute.Minimized)
{
writer.Write("=\"");
WriteTo(writer, HtmlEncoder, attribute.Value, escapeQuotes: true);
writer.Write('"');
}
}
if (tagHelperOutput.TagMode == TagMode.SelfClosing)
{
writer.Write(" /");
}
writer.Write('>');
}
if (isTagNameNullOrWhitespace || tagHelperOutput.TagMode == TagMode.StartTagAndEndTag)
{
WriteTo(writer, tagHelperOutput.PreContent);
if (tagHelperOutput.IsContentModified)
{
WriteTo(writer, tagHelperOutput.Content);
}
else if (tagHelperExecutionContext.ChildContentRetrieved)
{
var childContent = await tagHelperExecutionContext.GetChildContentAsync(useCachedResult: true);
WriteTo(writer, childContent);
}
else
{
await tagHelperExecutionContext.ExecuteChildContentAsync();
}
WriteTo(writer, tagHelperOutput.PostContent);
}
if (!isTagNameNullOrWhitespace && tagHelperOutput.TagMode == TagMode.StartTagAndEndTag)
{
writer.Write(string.Format(CultureInfo.InvariantCulture, "</{0}>", tagHelperOutput.TagName));
}
WriteTo(writer, tagHelperOutput.PostElement);
}
/// <summary>
/// Writes the specified <paramref name="value"/> with HTML encoding to <see cref="Output"/>.
/// </summary>
/// <param name="value">The <see cref="object"/> to write.</param>
public virtual void Write(object value)
{
WriteTo(Output, value);
}
/// <summary>
/// Writes the specified <paramref name="value"/> with HTML encoding to <paramref name="writer"/>.
/// </summary>
/// <param name="writer">The <see cref="TextWriter"/> instance to write to.</param>
/// <param name="value">The <see cref="object"/> to write.</param>
/// <remarks>
/// <paramref name="value"/>s of type <see cref="IHtmlContent"/> are written using
/// <see cref="IHtmlContent.WriteTo(TextWriter, IHtmlEncoder)"/>.
/// For all other types, the encoded result of <see cref="object.ToString"/> is written to the
/// <paramref name="writer"/>.
/// </remarks>
public virtual void WriteTo([NotNull] TextWriter writer, object value)
{
WriteTo(writer, HtmlEncoder, value, escapeQuotes: false);
}
/// <summary>
/// Writes the specified <paramref name="value"/> with HTML encoding to given <paramref name="writer"/>.
/// </summary>
/// <param name="writer">The <see cref="TextWriter"/> instance to write to.</param>
/// <param name="encoder">The <see cref="IHtmlEncoder"/> to use when encoding <paramref name="value"/>.</param>
/// <param name="value">The <see cref="object"/> to write.</param>
/// <param name="escapeQuotes">
/// If <c>true</c> escapes double quotes in a <paramref name="value"/> of type <see cref="HtmlString"/>.
/// Otherwise writes <see cref="HtmlString"/> values as-is.
/// </param>
/// <remarks>
/// <paramref name="value"/>s of type <see cref="IHtmlContent"/> are written using
/// <see cref="IHtmlContent.WriteTo(TextWriter, IHtmlEncoder)"/>.
/// For all other types, the encoded result of <see cref="object.ToString"/> is written to the
/// <paramref name="writer"/>.
/// </remarks>
public static void WriteTo(
[NotNull] TextWriter writer,
[NotNull] IHtmlEncoder encoder,
object value,
bool escapeQuotes)
{
if (value == null || value == HtmlString.Empty)
{
return;
}
var htmlContent = value as IHtmlContent;
if (htmlContent != null)
{
if (escapeQuotes)
{
// In this case the text likely came directly from the Razor source. Since the original string is
// an attribute value that may have been quoted with single quotes, must handle any double quotes
// in the value. Writing the value out surrounded by double quotes.
//
// This is really not optimal from a perf point of view, but it's the best we can do for right now.
using (var stringWriter = new StringWriter())
{
htmlContent.WriteTo(stringWriter, encoder);
var stringValue = stringWriter.ToString();
if (stringValue.Contains("\""))
{
stringValue = stringValue.Replace("\"", "&quot;");
}
writer.Write(stringValue);
return;
}
}
var htmlTextWriter = writer as HtmlTextWriter;
if (htmlTextWriter == null)
{
htmlContent.WriteTo(writer, encoder);
}
else
{
// This special case alows us to keep buffering as IHtmlContent until we get to the 'final'
// TextWriter.
htmlTextWriter.Write(htmlContent);
}
return;
}
WriteTo(writer, encoder, value.ToString());
}
/// <summary>
/// Writes the specified <paramref name="value"/> with HTML encoding to <paramref name="writer"/>.
/// </summary>
/// <param name="writer">The <see cref="TextWriter"/> instance to write to.</param>
/// <param name="value">The <see cref="string"/> to write.</param>
public virtual void WriteTo([NotNull] TextWriter writer, string value)
{
WriteTo(writer, HtmlEncoder, value);
}
private static void WriteTo(TextWriter writer, IHtmlEncoder encoder, string value)
{
if (!string.IsNullOrEmpty(value))
{
encoder.HtmlEncode(value, writer);
}
}
/// <summary>
/// Writes the specified <paramref name="value"/> without HTML encoding to <see cref="Output"/>.
/// </summary>
/// <param name="value">The <see cref="object"/> to write.</param>
public virtual void WriteLiteral(object value)
{
WriteLiteralTo(Output, value);
}
/// <summary>
/// Writes the specified <paramref name="value"/> without HTML encoding to the <paramref name="writer"/>.
/// </summary>
/// <param name="writer">The <see cref="TextWriter"/> instance to write to.</param>
/// <param name="value">The <see cref="object"/> to write.</param>
public virtual void WriteLiteralTo([NotNull] TextWriter writer, object value)
{
if (value != null)
{
WriteLiteralTo(writer, value.ToString());
}
}
/// <summary>
/// Writes the specified <paramref name="value"/> without HTML encoding to <see cref="Output"/>.
/// </summary>
/// <param name="writer">The <see cref="TextWriter"/> instance to write to.</param>
/// <param name="value">The <see cref="string"/> to write.</param>
public virtual void WriteLiteralTo([NotNull] TextWriter writer, string value)
{
if (!string.IsNullOrEmpty(value))
{
writer.Write(value);
}
}
public virtual void WriteAttribute(
string name,
[NotNull] PositionTagged<string> prefix,
[NotNull] PositionTagged<string> suffix,
params AttributeValue[] values)
{
WriteAttributeTo(Output, name, prefix, suffix, values);
}
public virtual void WriteAttributeTo(
[NotNull] TextWriter writer,
string name,
[NotNull] PositionTagged<string> prefix,
[NotNull] PositionTagged<string> suffix,
params AttributeValue[] values)
{
if (values.Length == 0)
{
// Explicitly empty attribute, so write the prefix
WritePositionTaggedLiteral(writer, prefix);
}
else if (IsSingleBoolFalseOrNullValue(values))
{
// Value is either null or the bool 'false' with no prefix; don't render the attribute.
return;
}
else if (UseAttributeNameAsValue(values))
{
var attributeValue = values[0];
var positionTaggedAttributeValue = attributeValue.Value;
WritePositionTaggedLiteral(writer, prefix);
var sourceLength = suffix.Position - positionTaggedAttributeValue.Position;
var nameAttributeValue = new AttributeValue(
attributeValue.Prefix,
new PositionTagged<object>(name, attributeValue.Value.Position),
literal: attributeValue.Literal);
// The value is just the bool 'true', write the attribute name instead of the string 'True'.
WriteAttributeValue(writer, nameAttributeValue, sourceLength);
}
else
{
// This block handles two cases.
// 1. Single value with prefix.
// 2. Multiple values with or without prefix.
WritePositionTaggedLiteral(writer, prefix);
for (var i = 0; i < values.Length; i++)
{
var attributeValue = values[i];
var positionTaggedAttributeValue = attributeValue.Value;
if (positionTaggedAttributeValue.Value == null)
{
// Nothing to write
continue;
}
var next = i == values.Length - 1 ?
suffix : // End of the list, grab the suffix
values[i + 1].Prefix; // Still in the list, grab the next prefix
// Calculate length of the source span by the position of the next value (or suffix)
var sourceLength = next.Position - attributeValue.Value.Position;
WriteAttributeValue(writer, attributeValue, sourceLength);
}
}
WritePositionTaggedLiteral(writer, suffix);
}
public void AddHtmlAttributeValues(
string attributeName,
TagHelperExecutionContext executionContext,
params AttributeValue[] values)
{
if (IsSingleBoolFalseOrNullValue(values))
{
// The first value was 'null' or 'false' indicating that we shouldn't render the attribute. The
// attribute is treated as a TagHelper attribute so it's only available in
// TagHelperContext.AllAttributes for TagHelper authors to see (if they want to see why the attribute
// was removed from TagHelperOutput.Attributes).
executionContext.AddTagHelperAttribute(
attributeName,
values[0].Value.Value?.ToString() ?? string.Empty);
return;
}
else if (UseAttributeNameAsValue(values))
{
executionContext.AddHtmlAttribute(attributeName, attributeName);
}
else
{
var valueBuffer = new StringCollectionTextWriter(Output.Encoding);
foreach (var value in values)
{
if (value.Value.Value == null)
{
// Skip null values
continue;
}
if (!string.IsNullOrEmpty(value.Prefix))
{
WriteLiteralTo(valueBuffer, value.Prefix);
}
WriteUnprefixedAttributeValueTo(valueBuffer, value);
}
using (var stringWriter = new StringWriter())
{
valueBuffer.Content.WriteTo(stringWriter, HtmlEncoder);
var htmlString = new HtmlString(stringWriter.ToString());
executionContext.AddHtmlAttribute(attributeName, htmlString);
}
}
}
public virtual string Href([NotNull] string contentPath)
{
if (_urlHelper == null)
{
_urlHelper = Context.RequestServices.GetRequiredService<IUrlHelper>();
}
return _urlHelper.Content(contentPath);
}
private void WriteAttributeValue(TextWriter writer, AttributeValue attributeValue, int sourceLength)
{
if (!string.IsNullOrEmpty(attributeValue.Prefix))
{
WritePositionTaggedLiteral(writer, attributeValue.Prefix);
}
BeginContext(attributeValue.Value.Position, sourceLength, isLiteral: attributeValue.Literal);
WriteUnprefixedAttributeValueTo(writer, attributeValue);
EndContext();
}
private void WriteUnprefixedAttributeValueTo(TextWriter writer, AttributeValue attributeValue)
{
var positionTaggedAttributeValue = attributeValue.Value;
var stringValue = positionTaggedAttributeValue.Value as string;
// The extra branching here is to ensure that we call the Write*To(string) overload where possible.
if (attributeValue.Literal && stringValue != null)
{
WriteLiteralTo(writer, stringValue);
}
else if (attributeValue.Literal)
{
WriteLiteralTo(writer, positionTaggedAttributeValue.Value);
}
else if (stringValue != null)
{
WriteTo(writer, stringValue);
}
else
{
WriteTo(writer, positionTaggedAttributeValue.Value);
}
}
private void WritePositionTaggedLiteral(TextWriter writer, string value, int position)
{
BeginContext(position, value.Length, isLiteral: true);
WriteLiteralTo(writer, value);
EndContext();
}
private void WritePositionTaggedLiteral(TextWriter writer, PositionTagged<string> value)
{
WritePositionTaggedLiteral(writer, value.Value, value.Position);
}
protected virtual HelperResult RenderBody()
{
if (RenderBodyDelegateAsync == null)
{
var message = Resources.FormatRazorPage_MethodCannotBeCalled(nameof(RenderBody), Path);
throw new InvalidOperationException(message);
}
_renderedBody = true;
return new HelperResult(RenderBodyDelegateAsync);
}
/// <summary>
/// Creates a named content section in the page that can be invoked in a Layout page using
/// <see cref="RenderSection(string)"/> or <see cref="RenderSectionAsync(string, bool)"/>.
/// </summary>
/// <param name="name">The name of the section to create.</param>
/// <param name="section">The <see cref="RenderAsyncDelegate"/> to execute when rendering the section.</param>
public void DefineSection([NotNull] string name, [NotNull] RenderAsyncDelegate section)
{
if (SectionWriters.ContainsKey(name))
{
throw new InvalidOperationException(Resources.FormatSectionAlreadyDefined(name));
}
SectionWriters[name] = section;
}
public bool IsSectionDefined([NotNull] string name)
{
EnsureMethodCanBeInvoked(nameof(IsSectionDefined));
return PreviousSectionWriters.ContainsKey(name);
}
/// <summary>
/// In layout pages, renders the content of the section named <paramref name="name"/>.
/// </summary>
/// <param name="name">The name of the section to render.</param>
/// <returns>Returns <see cref="HtmlString.Empty"/> to allow the <see cref="Write(object)"/> call to
/// succeed.</returns>
/// <remarks>The method writes to the <see cref="Output"/> and the value returned is a token
/// value that allows the Write (produced due to @RenderSection(..)) to succeed. However the
/// value does not represent the rendered content.</remarks>
public HtmlString RenderSection([NotNull] string name)
{
return RenderSection(name, required: true);
}
/// <summary>
/// In layout pages, renders the content of the section named <paramref name="name"/>.
/// </summary>
/// <param name="name">The section to render.</param>
/// <param name="required">Indicates if this section must be rendered.</param>
/// <returns>Returns <see cref="HtmlString.Empty"/> to allow the <see cref="Write(object)"/> call to
/// succeed.</returns>
/// <remarks>The method writes to the <see cref="Output"/> and the value returned is a token
/// value that allows the Write (produced due to @RenderSection(..)) to succeed. However the
/// value does not represent the rendered content.</remarks>
public HtmlString RenderSection([NotNull] string name, bool required)
{
EnsureMethodCanBeInvoked(nameof(RenderSection));
var task = RenderSectionAsyncCore(name, required);
return task.GetAwaiter().GetResult();
}
/// <summary>
/// In layout pages, asynchronously renders the content of the section named <paramref name="name"/>.
/// </summary>
/// <param name="name">The section to render.</param>
/// <returns>A <see cref="Task{HtmlString}"/> that on completion returns <see cref="HtmlString.Empty"/> that
/// allows the <see cref="Write(object)"/> call to succeed.</returns>
/// <remarks>The method writes to the <see cref="Output"/> and the value returned is a token
/// value that allows the Write (produced due to @RenderSection(..)) to succeed. However the
/// value does not represent the rendered content.</remarks>
public Task<HtmlString> RenderSectionAsync([NotNull] string name)
{
return RenderSectionAsync(name, required: true);
}
/// <summary>
/// In layout pages, asynchronously renders the content of the section named <paramref name="name"/>.
/// </summary>
/// <param name="name">The section to render.</param>
/// <returns>A <see cref="Task{HtmlString}"/> that on completion returns <see cref="HtmlString.Empty"/> that
/// allows the <see cref="Write(object)"/> call to succeed.</returns>
/// <remarks>The method writes to the <see cref="Output"/> and the value returned is a token
/// value that allows the Write (produced due to @RenderSection(..)) to succeed. However the
/// value does not represent the rendered content.</remarks>
/// <exception cref="InvalidOperationException">if <paramref name="required"/> is <c>true</c> and the section
/// was not registered using the <c>@section</c> in the Razor page.</exception>
public Task<HtmlString> RenderSectionAsync([NotNull] string name, bool required)
{
EnsureMethodCanBeInvoked(nameof(RenderSectionAsync));
return RenderSectionAsyncCore(name, required);
}
private async Task<HtmlString> RenderSectionAsyncCore(string sectionName, bool required)
{
if (_renderedSections.Contains(sectionName))
{
var message = Resources.FormatSectionAlreadyRendered(nameof(RenderSectionAsync), Path, sectionName);
throw new InvalidOperationException(message);
}
RenderAsyncDelegate renderDelegate;
if (PreviousSectionWriters.TryGetValue(sectionName, out renderDelegate))
{
_renderedSections.Add(sectionName);
await renderDelegate(Output);
// Return a token value that allows the Write call that wraps the RenderSection \ RenderSectionAsync
// to succeed.
return HtmlString.Empty;
}
else if (required)
{
// If the section is not found, and it is not optional, throw an error.
throw new InvalidOperationException(Resources.FormatSectionNotDefined(sectionName, Path));
}
else
{
// If the section is optional and not found, then don't do anything.
return null;
}
}
/// <summary>
/// Invokes <see cref="TextWriter.FlushAsync"/> on <see cref="Output"/> writing out any buffered
/// content to the <see cref="HttpResponse.Body"/>.
/// </summary>
/// <returns>A <see cref="Task{HtmlString}"/> that represents the asynchronous flush operation and on
/// completion returns a <see cref="HtmlString.Empty"/>.</returns>
/// <remarks>The value returned is a token value that allows FlushAsync to work directly in an HTML
/// section. However the value does not represent the rendered content.
/// This method also writes out headers, so any modifications to headers must be done before
/// <see cref="FlushAsync"/> is called. For example, call <see cref="SetAntiforgeryCookieAndHeader"/> to send
/// antiforgery cookie token and X-Frame-Options header to client before this method flushes headers out.
/// </remarks>
public async Task<HtmlString> FlushAsync()
{
// If there are active writing scopes then we should throw. Cannot flush content that has the potential to
// change.
if (_writerScopes.Count > 0)
{
throw new InvalidOperationException(
Resources.FormatRazorPage_CannotFlushWhileInAWritingScope(nameof(FlushAsync), Path));
}
// Calls to Flush are allowed if the page does not specify a Layout or if it is executing a section in the
// Layout.
if (!IsLayoutBeingRendered && !string.IsNullOrEmpty(Layout))
{
var message = Resources.FormatLayoutCannotBeRendered(Path, nameof(FlushAsync));
throw new InvalidOperationException(message);
}
await Output.FlushAsync();
return HtmlString.Empty;
}
/// <inheritdoc />
public void EnsureRenderedBodyOrSections()
{
// a) all sections defined for this page are rendered.
// b) if no sections are defined, then the body is rendered if it's available.
if (PreviousSectionWriters != null && PreviousSectionWriters.Count > 0)
{
var sectionsNotRendered = PreviousSectionWriters.Keys.Except(
_renderedSections,
StringComparer.OrdinalIgnoreCase);
if (sectionsNotRendered.Any())
{
var sectionNames = string.Join(", ", sectionsNotRendered);
throw new InvalidOperationException(Resources.FormatSectionsNotRendered(Path, sectionNames));
}
}
else if (RenderBodyDelegateAsync != null && !_renderedBody)
{
// There are no sections defined, but RenderBody was NOT called.
// If a body was defined, then RenderBody should have been called.
var message = Resources.FormatRenderBodyNotCalled(nameof(RenderBody), Path);
throw new InvalidOperationException(message);
}
}
public void BeginContext(int position, int length, bool isLiteral)
{
PageExecutionContext?.BeginContext(position, length, isLiteral);
}
public void EndContext()
{
PageExecutionContext?.EndContext();
}
/// <summary>
/// Sets antiforgery cookie and X-Frame-Options header on the response.
/// </summary>
/// <returns>A <see cref="HtmlString"/> that returns a <see cref="HtmlString.Empty"/>.</returns>
/// <remarks> Call this method to send antiforgery cookie token and X-Frame-Options header to client
/// before <see cref="FlushAsync"/> flushes the headers. </remarks>
public virtual HtmlString SetAntiforgeryCookieAndHeader()
{
var antiforgery = Context.RequestServices.GetRequiredService<IAntiforgery>();
antiforgery.SetCookieTokenAndHeader(Context);
return HtmlString.Empty;
}
private bool IsSingleBoolFalseOrNullValue(AttributeValue[] values)
{
if (values.Length == 1 && string.IsNullOrEmpty(values[0].Prefix) &&
(values[0].Value.Value is bool || values[0].Value.Value == null))
{
var attributeValue = values[0];
var positionTaggedAttributeValue = attributeValue.Value;
if (positionTaggedAttributeValue.Value == null || !(bool)positionTaggedAttributeValue.Value)
{
return true;
}
}
return false;
}
private bool UseAttributeNameAsValue(AttributeValue[] values)
{
// If the value is just the bool 'true', use the attribute name as the value.
return values.Length == 1 &&
string.IsNullOrEmpty(values[0].Prefix) &&
values[0].Value.Value is bool &&
(bool)values[0].Value.Value;
}
private void EnsureMethodCanBeInvoked(string methodName)
{
if (PreviousSectionWriters == null)
{
throw new InvalidOperationException(Resources.FormatRazorPage_MethodCannotBeCalled(methodName, Path));
}
}
}
}