private static string GetIndexerInvocation(Expression expression, ParameterExpression[] parameters)
{
Expression converted = Expression.Convert(expression, typeof(object));
ParameterExpression fakeParameter = Expression.Parameter(typeof(object), null);
Expression <Func <object, object> > lambda = Expression.Lambda <Func <object, object> >(converted, fakeParameter);
Func <object, object> func;
try
{
func = CachedExpressionCompiler.Process(lambda);
}
catch (InvalidOperationException ex)
{
throw new InvalidOperationException(
String.Format(
CultureInfo.CurrentCulture,
MvcResources.ExpressionHelper_InvalidIndexerExpression,
expression,
parameters[0].Name),
ex);
}
return("[" + Convert.ToString(func(null), CultureInfo.InvariantCulture) + "]");
}
public static ModelMetadata FromLambdaExpression <TParameter, TValue>(
Expression <Func <TParameter, TValue> > expression, ViewDataDictionary <TParameter> viewData)
{
if (expression == null)
{
throw new ArgumentNullException("expression");
}
if (viewData == null)
{
throw new ArgumentNullException("viewData");
}
string propertyName = null;
Type containerType = null;
bool 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)
{
// ArrayIndex always means a single-dimensional indexer; multi-dimensional indexer is a method call to Get()
case ExpressionType.ArrayIndex:
legalExpression = true;
break;
// Only legal method call is a single argument indexer/DefaultMember call
case ExpressionType.Call:
legalExpression = ExpressionHelper.IsSingleArgumentIndexer(expression.Body);
break;
// Property/field access is always legal
case ExpressionType.MemberAccess:
var memberExpression = (MemberExpression)expression.Body;
propertyName = memberExpression.Member is PropertyInfo ? memberExpression.Member.Name : null;
containerType = memberExpression.Expression.Type;
legalExpression = true;
break;
// Parameter expression means "model => model", so we delegate to FromModel
case ExpressionType.Parameter:
return(FromModel(viewData));
}
if (!legalExpression)
{
throw new InvalidOperationException(MvcResources.TemplateHelpers_TemplateLimitations);
}
TParameter container = viewData.Model;
Func <object> modelAccessor = () => {
try
{
return(CachedExpressionCompiler.Process(expression)(container));
}
catch (NullReferenceException)
{
return(null);
}
};
return(GetMetadataFromProvider(modelAccessor, typeof(TValue), propertyName, containerType));
}