protected override Expression VisitConstant(ConstantExpression node)
{
#if (DEBUGPRINT)
System.Diagnostics.Debug.Print("VisitConstant: {0}", node);
#endif
var expression = base.VisitConstant(node);
var type = node.Type;
if (IsNullableType(type))
{
var genericArgs = type.GetGenericArguments();
if ((genericArgs != null) && (genericArgs.Length == 1))
{
type = genericArgs[0];
}
}
if (type == typeof(byte[]))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromBinary((byte[])node.Value));
}
else if (type == typeof(bool))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromBoolean((bool?)node.Value));
}
else if (type == typeof(byte))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromByte((byte?)node.Value));
}
else if (type == typeof(DateTime))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromDateTime((DateTime?)node.Value));
}
else if (type == typeof(DateTimeOffset))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromDateTimeOffset((DateTimeOffset?)node.Value));
}
else if (type == typeof(decimal))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromDecimal((decimal?)node.Value));
}
else if (type == typeof(double))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromDouble((double?)node.Value));
}
else if (type == typeof(Guid))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromGuid((Guid?)node.Value));
}
else if (type == typeof(Int16))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromInt16((Int16?)node.Value));
}
else if (type == typeof(Int32))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromInt32((Int32?)node.Value));
}
else if (type.IsEnum)
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromInt32((Int32)node.Value));
}
else if (type == typeof(Int64))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromInt64((Int64?)node.Value));
}
else if (type == typeof(float))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromSingle((float?)node.Value));
}
else if (type == typeof(string))
{
MapExpressionToDbExpression(expression, DbConstantExpression.FromString((string)node.Value));
}
else
{
throw new NotImplementedException(string.Format("Unhandled Type of {0} for Constant value {1} in LambdaToDbExpressionVisitor.VisitConstant", node.Type.Name, node.Value ?? "null"));
}
return(expression);
}
// This is called for any navigation property reference so we can apply filters for those entities here.
// That includes any navigation properties referenced in functions (.Where() clauses) and also any
// child entities that are .Include()'d.
public override DbExpression Visit(DbPropertyExpression expression)
{
#if DEBUG_VISITS
System.Diagnostics.Debug.Print("Visit(DbPropertyExpression): EdmType.Name={0}", expression.ResultType.ModelTypeUsage.EdmType.Name);
#endif
var baseResult = base.Visit(expression);
var basePropertyResult = baseResult as DbPropertyExpression;
if (basePropertyResult == null)
{
return(baseResult); // base.Visit changed type!
}
var navProp = basePropertyResult.Property as NavigationProperty;
if (navProp != null)
{
var targetEntityType = navProp.ToEndMember.GetEntityType();
string entityName = targetEntityType.Name;
var containers = _ObjectContext.MetadataWorkspace.GetItems <EntityContainer>(DataSpace.CSpace).First();
var filterList = FindFiltersForEntitySet(targetEntityType.MetadataProperties, containers);
if (filterList.Any())
{
// If the expression contains a collection (i.e. the child property is an IEnumerable), we can bind directly to it.
// Otherwise, we have to create a DbScanExpression over the ResultType in order to bind.
if (baseResult.ResultType.EdmType.BuiltInTypeKind == BuiltInTypeKind.CollectionType)
{
var binding = DbExpressionBuilder.Bind(baseResult);
var newFilterExpression = BuildFilterExpressionWithDynamicFilters(entityName, filterList, binding, null);
if (newFilterExpression != null)
{
// If not null, a new DbFilterExpression has been created with our dynamic filters.
return(newFilterExpression);
}
}
else if (baseResult.ResultType.EdmType.BuiltInTypeKind == BuiltInTypeKind.EntityType)
{
if (DoesNotSupportElementMethod(_DbContext))
{
// Oracle and MySQL do not support the "newFilterExpression.Element()" method that we need to call
// at the end of this block. Oracle *MAY* support it in a newer release but not sure
// (see https://community.oracle.com/message/10168766#10168766).
// But users may not have the option of upgrading their database so decided to try to support it.
// If we find it is supported by newer versions, can detect those versions and allow the normal handling.
// To apply any necessary filters to these entities, we're going to have to do it using SSpace.
// These entities will be visited via the DbScan visit method so we will apply filters there.
// If one of those filters then references a child property, the filter will fail.
return(baseResult);
}
var entitySet = containers.EntitySets.FirstOrDefault(e => e.ElementType.Name == baseResult.ResultType.EdmType.Name);
if (entitySet == null)
{
#if (DEBUG)
throw new ApplicationException(string.Format("EntitySet not found for {0} - this is a known issue when using TPT", baseResult.ResultType.EdmType.Name));
#else
return(baseResult);
#endif
}
var scanExpr = DbExpressionBuilder.Scan(entitySet);
var binding = DbExpressionBuilder.Bind(scanExpr);
// Build the join conditions that are needed to join from the source object (basePropertyResult.Instance)
// to the child object (the scan expression we just creating the binding for).
// These conditions will be and'd with the filter conditions.
var associationType = navProp.RelationshipType as AssociationType;
if (associationType == null)
{
throw new ApplicationException(string.Format("Unable to find AssociationType on navigation property of single child property {0} in type {1}", navProp.Name, navProp.DeclaringType.FullName));
}
if (associationType.Constraint == null)
{
// KNOWN_ISSUE:
// If this happens, the model does not contain the foreign key (the "id" property). EF will automatically generate
// it based on naming rules when generating the SSpace/database models but does not expose the Constraint here in the
// AssociationType. In order for us to be able to generate the conditions correctly, those Foreign Keys need to be
// specified on the model. To fix/handle this, we would need to examine the SSpace Association Sets (which do have
// these relations!!) to try to map that information back to CSpace to figure out the correct properties of the FK conditions.
// or...the models just need to contain the necessary "ID" properties for the FK relations so that they are available here
// (in CSpace) for us to generate the necessary join conditions.
throw new ApplicationException(string.Format("FK Constriant not found for association '{0}' - must directly specify foreign keys on model to be able to apply this filter", associationType.FullName));
}
// Figure out if the "baseResults" are the from side or to side of the constraint so we can create the properties correctly
bool baseResultIsFromRole = (basePropertyResult.Instance.ResultType.EdmType == ((AssociationEndMember)associationType.Constraint.FromRole).GetEntityType());
DbExpression joinCondition = null;
for (int i = 0; i < associationType.Constraint.FromProperties.Count; i++)
{
var prop1 = DbExpressionBuilder.Property(basePropertyResult.Instance, baseResultIsFromRole ? associationType.Constraint.FromProperties[i] : associationType.Constraint.ToProperties[i]);
var prop2 = DbExpressionBuilder.Property(binding.Variable, baseResultIsFromRole ? associationType.Constraint.ToProperties[i] : associationType.Constraint.FromProperties[i]);
var condition = prop1.Equal(prop2) as DbExpression;
joinCondition = (joinCondition == null) ? condition : joinCondition.And(condition);
}
// Translate the filter predicate into a DbExpression bound to the Scan expression of the target entity set.
// Those conditions are then and'd with the join conditions necessary to join the target table with the source table.
var newFilterExpression = BuildFilterExpressionWithDynamicFilters(entityName, filterList, binding, joinCondition);
if (newFilterExpression != null)
{
// Converts the collection results into a single row. The expected output is a single item so EF will
// then populate the results of that query into the property in the model.
// The resulting SQL will be a normal "left outer join" just as it would normally be except that our
// filter predicate conditions will be included with the normal join conditions.
// MySQL needs this Limit() applied here or it throws an error saying:
// Unable to cast object of type 'MySql.Data.Entity.SelectStatement' to type 'MySql.Data.Entity.LiteralFragment'.
// But don't do that unless necessary because it produces extra "outer apply" sub queries in MS SQL.
// This trick does not work for Oracle...
if (_DbContext.IsMySql())
{
return(newFilterExpression.Limit(DbConstantExpression.FromInt32(1)).Element());
}
return(newFilterExpression.Element());
}
}
}
}
return(baseResult);
}
