public string RenderToStringAsync(string viewName, object model)
{
var httpContext = new DefaultHttpContext {
RequestServices = _serviceProvider
};
var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
using (var sw = new StringWriter())
{
var viewResult = _razorViewEngine.FindView(actionContext, viewName, false);
if (viewResult.View == null)
{
throw new ArgumentNullException($"{viewName} does not match any available view");
}
var viewDictionary = new ViewDataDictionary(new EmptyModelMetadataProvider(), new ModelStateDictionary())
{
Model = model
};
var viewContext = new ViewContext(
actionContext,
viewResult.View,
viewDictionary,
new TempDataDictionary(actionContext.HttpContext, _tempDataProvider),
sw,
new HtmlHelperOptions()
);
viewResult.View.RenderAsync(viewContext);
return(sw.ToString());
}
}
public virtual async Task ExecuteAsync(ActionContext context, ViewComponentResult result)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
if (result == null)
{
throw new ArgumentNullException(nameof(result));
}
var response = context.HttpContext.Response;
var viewData = result.ViewData;
if (viewData == null)
{
viewData = new ViewDataDictionary(_modelMetadataProvider, context.ModelState);
}
var tempData = result.TempData;
if (tempData == null)
{
tempData = _tempDataDictionaryFactory.GetTempData(context.HttpContext);
}
ResponseContentTypeHelper.ResolveContentTypeAndEncoding(
result.ContentType,
response.ContentType,
(ViewExecutor.DefaultContentType, Encoding.UTF8),
MediaType.GetEncoding,
out var resolvedContentType,
out var resolvedContentTypeEncoding);
response.ContentType = resolvedContentType;
if (result.StatusCode != null)
{
response.StatusCode = result.StatusCode.Value;
}
await using var writer = _writerFactory.CreateWriter(response.Body, resolvedContentTypeEncoding);
var viewContext = new ViewContext(
context,
NullView.Instance,
viewData,
tempData,
writer,
_htmlHelperOptions);
OnExecuting(viewContext);
// IViewComponentHelper is stateful, we want to make sure to retrieve it every time we need it.
var viewComponentHelper = context.HttpContext.RequestServices.GetRequiredService <IViewComponentHelper>();
(viewComponentHelper as IViewContextAware)?.Contextualize(viewContext);
var viewComponentResult = await GetViewComponentResult(viewComponentHelper, _logger, result);
if (viewComponentResult is ViewBuffer viewBuffer)
{
// In the ordinary case, DefaultViewComponentHelper will return an instance of ViewBuffer. We can simply
// invoke WriteToAsync on it.
await viewBuffer.WriteToAsync(writer, _htmlEncoder);
await writer.FlushAsync();
}
else
{
await using var bufferingStream = new FileBufferingWriteStream();
await using (var intermediateWriter = _writerFactory.CreateWriter(bufferingStream, resolvedContentTypeEncoding))
{
viewComponentResult.WriteTo(intermediateWriter, _htmlEncoder);
}
await bufferingStream.DrainBufferAsync(response.Body);
}
}
public ViewDataDictionary(ViewDataDictionary source, object?model)
: base(source, model, declaredModelType: typeof(TModel))
{
}
public ViewDataDictionary(ViewDataDictionary source)
: base(source, declaredModelType: typeof(TModel))
{
}
/// <summary>
/// Initializes a new instance of the <see cref="ViewDataDictionary"/> class based entirely on an existing
/// instance.
/// </summary>
/// <param name="source"><see cref="ViewDataDictionary"/> instance to copy initial values from.</param>
/// <remarks>
/// <para>
/// For use when copying a <see cref="ViewDataDictionary"/> instance and the declared <see cref="Model"/>
/// <see cref="Type"/> will not change e.g. when copying from a <see cref="ViewDataDictionary{TModel}"/>
/// instance to a base <see cref="ViewDataDictionary"/> instance.
/// </para>
/// <para>
/// This constructor should not be used in any context where <see cref="Model"/> may be set to a value
/// incompatible with the declared type of <paramref name="source"/>.
/// </para>
/// </remarks>
public ViewDataDictionary(ViewDataDictionary source)
: this(source, source.Model, source._declaredModelType)
{
}
/// <summary>
/// Initializes a new instance of the <see cref="ViewDataDictionary"/> class based in part on an existing
/// instance. This constructor is careful to avoid exceptions <see cref="SetModel"/> may throw when
/// <paramref name="model"/> is <c>null</c>.
/// </summary>
/// <param name="source"><see cref="ViewDataDictionary"/> instance to copy initial values from.</param>
/// <param name="model">Value for the <see cref="Model"/> property.</param>
/// <param name="declaredModelType">
/// <see cref="Type"/> of <see cref="Model"/> values expected. Used to set <see cref="ModelMetadata"/>.
/// </param>
/// <remarks>
/// <para>
/// For use when copying a <see cref="ViewDataDictionary"/> instance and new instance's declared
/// <see cref="Model"/> <see cref="Type"/> and <see cref="Model"/> are known.
/// </para>
/// <para>
/// This constructor may <c>throw</c> if <paramref name="model"/> is non-<c>null</c> and incompatible with
/// <paramref name="declaredModelType"/>.
/// </para>
/// </remarks>
// This is the core constructor called when Model is known.
protected ViewDataDictionary(ViewDataDictionary source, object model, Type declaredModelType)
: this(source._metadataProvider,
source.ModelState,
declaredModelType,
data : new CopyOnWriteDictionary <string, object>(source, StringComparer.OrdinalIgnoreCase),
templateInfo : new TemplateInfo(source.TemplateInfo))
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
// A non-null Model must always be assignable to both _declaredModelType and ModelMetadata.ModelType.
//
// ModelMetadata.ModelType should also be assignable to _declaredModelType. Though corner cases exist such
// as a ViewDataDictionary<List<int>> holding information about an IEnumerable<int> property (because an
// @model directive matched the runtime type though the view's name did not), we'll throw away the property
// metadata in those cases -- preserving invariant that ModelType can be assigned to _declaredModelType.
//
// More generally, since defensive copies to base VDD and VDD<object> abound, it's important to preserve
// metadata despite _declaredModelType changes.
var modelType = model?.GetType();
var modelOrDeclaredType = modelType ?? declaredModelType;
if (source.ModelMetadata.MetadataKind == ModelMetadataKind.Type &&
source.ModelMetadata.ModelType == typeof(object) &&
modelOrDeclaredType != typeof(object))
{
// Base ModelMetadata on new type when there's no property information to preserve and type changes to
// something besides typeof(object).
ModelExplorer = _metadataProvider.GetModelExplorerForType(modelOrDeclaredType, model);
}
else if (!declaredModelType.IsAssignableFrom(source.ModelMetadata.ModelType))
{
// Base ModelMetadata on new type when existing metadata is incompatible with the new declared type.
ModelExplorer = _metadataProvider.GetModelExplorerForType(modelOrDeclaredType, model);
}
else if (modelType != null && !source.ModelMetadata.ModelType.IsAssignableFrom(modelType))
{
// Base ModelMetadata on new type when new model is incompatible with the existing metadata.
ModelExplorer = _metadataProvider.GetModelExplorerForType(modelType, model);
}
else if (object.ReferenceEquals(model, source.ModelExplorer.Model))
{
// Source's ModelExplorer is already exactly correct.
ModelExplorer = source.ModelExplorer;
}
else
{
// The existing metadata is compatible with the value and declared type but it's a new value.
ModelExplorer = new ModelExplorer(
_metadataProvider,
source.ModelExplorer.Container,
source.ModelMetadata,
model);
}
// Ensure the given Model is compatible with _declaredModelType. Do not do this one of the following
// special cases:
// - Constructing a ViewDataDictionary<TModel> where TModel is a non-Nullable value type. This may for
// example occur when activating a RazorPage<int> and the container is null.
// - Constructing a ViewDataDictionary<object> immediately before overwriting ModelExplorer with correct
// information. See TemplateBuilder.Build().
if (model != null)
{
EnsureCompatible(model);
}
}
/// <summary>
/// Initializes a new instance of the <see cref="ViewDataDictionary"/> class based in part on an existing
/// instance.
/// </summary>
/// <param name="source"><see cref="ViewDataDictionary"/> instance to copy initial values from.</param>
/// <param name="declaredModelType">
/// <see cref="Type"/> of <see cref="Model"/> values expected. Used to set <see cref="ModelMetadata"/>.
/// </param>
/// <remarks>
/// <para>
/// For use when copying a <see cref="ViewDataDictionary"/> instance and new instance's declared
/// <see cref="Model"/> <see cref="Type"/> is known but <see cref="Model"/> should be copied from the existing
/// instance e.g. when copying from a base <see cref="ViewDataDictionary"/> instance to a
/// <see cref="ViewDataDictionary{TModel}"/> instance.
/// </para>
/// <para>
/// This constructor may <c>throw</c> if <c>source.Model</c> is non-<c>null</c> and incompatible with
/// <paramref name="declaredModelType"/>. Pass <c>model: null</c> to
/// <see cref="ViewDataDictionary(ViewDataDictionary, object, Type)"/> to ignore <c>source.Model</c>.
/// </para>
/// </remarks>
protected ViewDataDictionary(ViewDataDictionary source, Type declaredModelType)
: this(source, model : source.Model, declaredModelType : declaredModelType)
{
}
