private static void InsertIndexerInvocationText(
StringBuilder builder,
Expression indexExpression,
LambdaExpression parentExpression)
{
if (builder == null)
{
throw new ArgumentNullException(nameof(builder));
}
if (indexExpression == null)
{
throw new ArgumentNullException(nameof(indexExpression));
}
if (parentExpression == null)
{
throw new ArgumentNullException(nameof(parentExpression));
}
if (parentExpression.Parameters == null)
{
throw new ArgumentException(Resources.FormatPropertyOfTypeCannotBeNull(
nameof(parentExpression.Parameters),
nameof(parentExpression)));
}
var converted = Expression.Convert(indexExpression, typeof(object));
var fakeParameter = Expression.Parameter(typeof(object), null);
var lambda = Expression.Lambda <Func <object, object> >(converted, fakeParameter);
Func <object, object> func;
try
{
func = CachedExpressionCompiler.Process(lambda);
}
catch (InvalidOperationException ex)
{
var parameters = parentExpression.Parameters.ToArray();
throw new InvalidOperationException(
Resources.FormatExpressionHelper_InvalidIndexerExpression(indexExpression, parameters[0].Name),
ex);
}
builder.Insert(0, ']');
builder.Insert(0, Convert.ToString(func(null), CultureInfo.InvariantCulture));
builder.Insert(0, '[');
}
public static ModelExplorer FromLambdaExpression <TModel, TResult>(
Expression <Func <TModel, TResult> > expression,
ViewDataDictionary <TModel> viewData,
IModelMetadataProvider metadataProvider)
{
if (expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if (viewData == null)
{
throw new ArgumentNullException(nameof(viewData));
}
string propertyName = null;
Type containerType = null;
var legalExpression = false;
// Need to verify the expression is valid; it needs to at least end in something
// that we can convert to a meaningful string for model binding purposes
switch (expression.Body.NodeType)
{
case ExpressionType.ArrayIndex:
// ArrayIndex always means a single-dimensional indexer;
// multi-dimensional indexer is a method call to Get().
legalExpression = true;
break;
case ExpressionType.Call:
// Only legal method call is a single argument indexer/DefaultMember call
legalExpression = ExpressionHelper.IsSingleArgumentIndexer(expression.Body);
break;
case ExpressionType.MemberAccess:
// Property/field access is always legal
var memberExpression = (MemberExpression)expression.Body;
propertyName = memberExpression.Member is PropertyInfo ? memberExpression.Member.Name : null;
containerType = memberExpression.Expression.Type;
legalExpression = true;
break;
case ExpressionType.Parameter:
// Parameter expression means "model => model", so we delegate to FromModel
return(FromModel(viewData, metadataProvider));
}
if (!legalExpression)
{
throw new InvalidOperationException(Resources.TemplateHelpers_TemplateLimitations);
}
Func <object, object> modelAccessor = (container) =>
{
try
{
return(CachedExpressionCompiler.Process(expression)((TModel)container));
}
catch (NullReferenceException)
{
return(null);
}
};
ModelMetadata metadata;
if (propertyName == null)
{
// Ex:
// m => 5 (arbitrary expression)
// m => foo (arbitrary expression)
// m => m.Widgets[0] (expression ending with non-property-access)
metadata = metadataProvider.GetMetadataForType(typeof(TResult));
}
else
{
// Ex:
// m => m.Color (simple property access)
// m => m.Color.Red (nested property access)
// m => m.Widgets[0].Size (expression ending with property-access)
metadata = metadataProvider.GetMetadataForType(containerType).Properties[propertyName];
}
return(viewData.ModelExplorer.GetExplorerForExpression(metadata, modelAccessor));
}
public static ModelExplorer FromLambdaExpression <TModel, TResult>(
Expression <Func <TModel, TResult> > expression,
ViewDataDictionary <TModel> viewData,
IModelMetadataProvider metadataProvider)
{
if (expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if (viewData == null)
{
throw new ArgumentNullException(nameof(viewData));
}
string propertyName = null;
Type containerType = null;
var legalExpression = false;
// Need to verify the expression is valid; it needs to at least end in something
// that we can convert to a meaningful string for model binding purposes
switch (expression.Body.NodeType)
{
case ExpressionType.ArrayIndex:
// ArrayIndex always means a single-dimensional indexer;
// multi-dimensional indexer is a method call to Get().
legalExpression = true;
break;
case ExpressionType.Call:
// Only legal method call is a single argument indexer/DefaultMember call
legalExpression = ExpressionHelper.IsSingleArgumentIndexer(expression.Body);
break;
case ExpressionType.MemberAccess:
// Property/field access is always legal
var memberExpression = (MemberExpression)expression.Body;
propertyName = memberExpression.Member is PropertyInfo ? memberExpression.Member.Name : null;
if (string.Equals(propertyName, "Model", StringComparison.Ordinal) &&
memberExpression.Type == typeof(TModel) &&
memberExpression.Expression.NodeType == ExpressionType.Constant)
{
// Special case the Model property in RazorPage<TModel>. (m => Model) should behave identically
// to (m => m). But do the more complicated thing for (m => m.Model) since that is a slightly
// different beast.)
return(FromModel(viewData, metadataProvider));
}
// memberExpression.Expression can be null when this is a static field or property.
//
// This can be the case if the expression is like (m => Person.Name) where Name is a static field
// or property on the Person type.
containerType = memberExpression.Expression?.Type;
legalExpression = true;
break;
case ExpressionType.Parameter:
// Parameter expression means "model => model", so we delegate to FromModel
return(FromModel(viewData, metadataProvider));
}
if (!legalExpression)
{
throw new InvalidOperationException(Resources.TemplateHelpers_TemplateLimitations);
}
object modelAccessor(object container)
{
var model = (TModel)container;
var cachedFunc = CachedExpressionCompiler.Process(expression);
if (cachedFunc != null)
{
return(cachedFunc(model));
}
var func = expression.Compile();
try
{
return(func(model));
}
catch (NullReferenceException)
{
return(null);
}
}
ModelMetadata metadata = null;
if (containerType != null && propertyName != null)
{
// Ex:
// m => m.Color (simple property access)
// m => m.Color.Red (nested property access)
// m => m.Widgets[0].Size (expression ending with property-access)
metadata = metadataProvider.GetMetadataForType(containerType).Properties[propertyName];
}
if (metadata == null)
{
// Ex:
// m => 5 (arbitrary expression)
// m => foo (arbitrary expression)
// m => m.Widgets[0] (expression ending with non-property-access)
//
// This can also happen for any case where we cannot retrieve a model metadata.
// This will happen for:
// - fields
// - statics
// - non-visibility (internal/private)
metadata = metadataProvider.GetMetadataForType(typeof(TResult));
Debug.Assert(metadata != null);
}
return(viewData.ModelExplorer.GetExplorerForExpression(metadata, modelAccessor));
}
