/// <summary>
/// Starts a new writing scope and optionally overrides <see cref="HtmlEncoder"/> within that scope.
/// </summary>
/// <param name="encoder">
/// The <see cref="System.Text.Encodings.Web.HtmlEncoder"/> to use when this <see cref="RazorPage"/> handles
/// non-<see cref="IHtmlContent"/> C# expressions. If <c>null</c>, does not change <see cref="HtmlEncoder"/>.
/// </param>
/// <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(HtmlEncoder encoder)
{
var buffer = new ViewBuffer(BufferScope, Key, ViewBuffer.TagHelperPageSize);
TagHelperScopes.Push(new TagHelperScopeInfo(buffer, HtmlEncoder, PageContext.Writer));
// If passed an HtmlEncoder, override the property.
if (encoder != null)
{
HtmlEncoder = encoder;
}
// We need to replace the ViewContext's Writer to ensure that all content (including content written
// from HTML helpers) is redirected.
PageContext.Writer = new ViewBufferTextWriter(buffer, PageContext.Writer.Encoding);
}
/// <summary>
/// Ends the current writing scope that was started by calling <see cref="StartTagHelperWritingScope"/>.
/// </summary>
/// <returns>The buffered <see cref="TagHelperContent"/>.</returns>
public TagHelperContent EndTagHelperWritingScope()
{
if (TagHelperScopes.Count == 0)
{
throw new InvalidOperationException("There is no active scope to write");
}
var scopeInfo = TagHelperScopes.Pop();
// Get the content written during the current scope.
var tagHelperContent = new DefaultTagHelperContent();
tagHelperContent.AppendHtml(scopeInfo.Buffer);
// Restore previous scope.
HtmlEncoder = scopeInfo.HtmlEncoder;
PageContext.Writer = scopeInfo.Writer;
return(tagHelperContent);
}
/// <summary>
/// Ends the current writing scope that was started by calling <see cref="StartTagHelperWritingScope"/>.
/// </summary>
/// <returns>The buffered <see cref="TagHelperContent"/>.</returns>
public TagHelperContent EndTagHelperWritingScope()
{
if (TagHelperScopes.Count == 0)
{
throw new InvalidOperationException(Resources.RazorPage_ThereIsNoActiveWritingScopeToEnd);
}
var scopeInfo = TagHelperScopes.Pop();
// Get the content written during the current scope.
var tagHelperContent = new DefaultTagHelperContent();
tagHelperContent.AppendHtml(scopeInfo.Buffer);
// Restore previous scope.
HtmlEncoder = scopeInfo.HtmlEncoder;
ViewContext.Writer = scopeInfo.Writer;
return(tagHelperContent);
}
