private static string GetIndexerInvocation(
Expression expression,
ParameterExpression[] parameters)
{
if (expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if (parameters == null)
{
throw new ArgumentNullException(nameof(parameters));
}
var converted = Expression.Convert(expression, 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)
{
throw new InvalidOperationException(
Resources.FormatExpressionHelper_InvalidIndexerExpression(expression, parameters[0].Name),
ex);
}
return("[" + Convert.ToString(func(null), CultureInfo.InvariantCulture) + "]");
}
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));
}