private Expression CreateTypeCheckExpression(MemberExpression memberExpression, Expression typeValueExpression)
{
string typeName;
if (typeValueExpression.NodeType == ExpressionType.Constant)
{
typeName = (typeValueExpression as ConstantExpression).Value.ToString();
}
else if (typeValueExpression.NodeType == ExpressionType.MemberAccess)
{
typeName = GetMemberValue((typeValueExpression as MemberExpression)).ToString();
}
else
{
throw new NotSupportedException("Type name must be either a string literal or constant class member.");
}
HashSet <int> typeDbIds;
ModelType.TryGetNotAbstractIncludingDerivedTypeDbIds(new string[] { typeName }, out typeDbIds);
bool nullable = IsNullable(memberExpression.Type);
Expression newMemberExpression = memberExpression;
if (nullable)
{
newMemberExpression = Expression.Convert(newMemberExpression, typeof(int));
}
Expression typeCheckExpression = Expression.Call(
Expression.Constant(typeDbIds),
typeDbIds.GetType().GetMethod(nameof(HashSet <int> .Contains)),
newMemberExpression);
if (nullable)
{
Expression notNullExpression = Expression.MakeBinary(ExpressionType.NotEqual, memberExpression, Expression.Constant(null));
typeCheckExpression = Expression.AndAlso(notNullExpression, typeCheckExpression);
}
return(typeCheckExpression);
}
protected override Expression VisitTypeBinary(TypeBinaryExpression node)
{
var expression = Visit(node.Expression);
if (expression.Type != node.Expression.Type)
{
HashSet <int> typeDbIds = null;
Expression <Func <int> > x = () => typeDbIds.Count;
ModelType.TryGetNotAbstractIncludingDerivedTypeDbIds(new string[] { node.TypeOperand.FullName }, out typeDbIds);
Expression typePropAccess = Expression.MakeMemberAccess(
expression,
typeof(TDbEntity).GetProperty(nameof(IDbEntity.Type), BindingFlags.Instance | BindingFlags.Public));
return(Expression.Call(
Expression.Constant(typeDbIds),
typeDbIds.GetType().GetMethod(nameof(HashSet <int> .Contains)),
typePropAccess));
}
return(base.VisitTypeBinary(node));
}
