private Expression GetPredicateBody(HttpRequestMessage request, ParameterExpression param)
{
Expression workingExpr = null;
var type = param.Type;
var queryPairs = request.GetQueryNameValuePairs();
foreach (var queryPair in queryPairs)
{
if (String.IsNullOrWhiteSpace(queryPair.Key))
{
continue;
}
if (!queryPair.Key.StartsWith("filter."))
{
continue;
}
if (queryPair.Key.StartsWith("filter.calculated."))
{
continue;
}
var filterField = queryPair.Key.Substring(7); // Skip "filter."
IResourceTypeRegistration registration;
try
{
registration = _resourceTypeRegistry.GetRegistrationForType(type);
}
catch (TypeRegistrationNotFoundException)
{
throw JsonApiException.CreateForBadRequest("No registration exists for the specified type");
}
var expr = GetPredicate(filterField, registration, param, queryPair.Value);
workingExpr = workingExpr == null ? expr : Expression.AndAlso(workingExpr, expr);
}
return(workingExpr ?? Expression.Constant(true)); // No filters, so return everything
}
private Expression GetPredicate(string filterField, IResourceTypeRegistration registration, ParameterExpression param, string queryValue)
{
if (filterField == "id")
{
return(GetPredicateBodyForProperty(registration.IdProperty, queryValue, param));
}
var resourceTypeField = registration.GetFieldByName(filterField);
if (resourceTypeField == null)
{
throw JsonApiException.CreateForBadRequest(
string.Format("No attribute {0} exists on the specified type.", filterField));
}
if (string.IsNullOrWhiteSpace(queryValue))
{
queryValue = null;
}
// See if it is a field property
var fieldModelProperty = resourceTypeField as ResourceTypeAttribute;
if (fieldModelProperty != null)
{
return(GetPredicateBodyForField(fieldModelProperty, queryValue, param));
}
// See if it is a relationship property
var relationshipModelProperty = resourceTypeField as ResourceTypeRelationship;
if (relationshipModelProperty != null)
{
return(GetPredicateBodyForRelationship(relationshipModelProperty, queryValue, param));
}
throw JsonApiException.CreateForBadRequest(
string.Format("The attribute {0} is unsupported for filtering.", filterField));
}
private Expression GetPredicateBodyForRelationship(ResourceTypeRelationship resourceTypeProperty, string queryValue, ParameterExpression param)
{
var relatedType = resourceTypeProperty.RelatedType;
PropertyInfo relatedIdProperty;
try
{
var registration = _resourceTypeRegistry.GetRegistrationForType(relatedType);
relatedIdProperty = registration.IdProperty;
}
catch (TypeRegistrationNotFoundException)
{
throw JsonApiException.CreateForBadRequest("No registration exists for the specified type");
}
var prop = resourceTypeProperty.Property;
if (resourceTypeProperty.IsToMany)
{
var propertyExpr = Expression.Property(param, prop);
if (string.IsNullOrWhiteSpace(queryValue))
{
var leftExpr = Expression.Equal(propertyExpr, Expression.Constant(null));
var asQueryableCallExpr = Expression.Call(
typeof(Queryable),
"AsQueryable",
new[] { relatedType },
propertyExpr);
var anyCallExpr = Expression.Call(
typeof(Queryable),
"Any",
new[] { relatedType },
asQueryableCallExpr);
var rightExpr = Expression.Not(anyCallExpr);
return(Expression.OrElse(leftExpr, rightExpr));
}
else
{
var leftExpr = Expression.NotEqual(propertyExpr, Expression.Constant(null));
var idValue = queryValue.Trim();
var idExpr = Expression.Constant(idValue);
var anyParam = Expression.Parameter(relatedType);
var relatedIdPropertyExpr = Expression.Property(anyParam, relatedIdProperty);
var relatedIdPropertyEqualsIdExpr = Expression.Equal(relatedIdPropertyExpr, idExpr);
var anyPredicateExpr = Expression.Lambda(relatedIdPropertyEqualsIdExpr, anyParam);
var asQueryableCallExpr = Expression.Call(
typeof(Queryable),
"AsQueryable",
new[] { relatedType },
propertyExpr);
var rightExpr = Expression.Call(
typeof(Queryable),
"Any",
new[] { relatedType },
asQueryableCallExpr,
anyPredicateExpr);
return(Expression.AndAlso(leftExpr, rightExpr));
}
}
else
{
var propertyExpr = Expression.Property(param, prop);
if (string.IsNullOrWhiteSpace(queryValue))
{
return(Expression.Equal(propertyExpr, Expression.Constant(null)));
}
var leftExpr = Expression.NotEqual(propertyExpr, Expression.Constant(null));
var idValue = queryValue.Trim();
var idExpr = Expression.Constant(idValue);
var relatedIdPropertyExpr = Expression.Property(propertyExpr, relatedIdProperty);
var rightExpr = Expression.Equal(relatedIdPropertyExpr, idExpr);
return(Expression.AndAlso(leftExpr, rightExpr));
}
}
