/// <summary>
/// Resolves dependency constraints.
/// </summary>
/// <param name="entity">The entity.</param>
/// <param name="entitiesToDelete">The entities to delete.</param>
/// <returns>Returns a list of contraints.</returns>
protected virtual List <string> ResolveDependencyConstraints(Entity entity, List <Entity> entitiesToDelete)
{
var constraints = new List <string>();
var entityType = entity.GetType();
var entityMetadataList = EntityMetadataResolver.EntityMetadata.Where(x => x.Fields.Any(y => y.FieldType == entityType.Name && y.Mandatory));
foreach (var entityMetadata in entityMetadataList)
{
var currentType = EntityMetadataResolver.GetEntityType(entityMetadata);
var fields = entityMetadata.Fields.Where(x => x.FieldType == entityType.Name && x.Mandatory);
var parameter = Expression.Parameter(currentType, "x");
Expression resultExpression = null;
foreach (var field in fields)
{
var body = Expression.Equal(Expression.Property(parameter, field.Name), Expression.Constant(entity.Id));
resultExpression = resultExpression == null ? body : Expression.OrElse(resultExpression, body);
}
var finalExpression = Expression.Lambda(resultExpression, parameter);
var queryable = new QueryProvider(this).CreateQuery(Expression.Constant(null, typeof(IQueryable <>).MakeGenericType(currentType)));
var methodInfo = typeof(Queryable).GetMethods().FirstOrDefault(x => x.Name == "Where").MakeGenericMethod(currentType);
var methodCall = Expression.Call(methodInfo, queryable.Expression, finalExpression);
queryable = queryable.Provider.CreateQuery(methodCall);
var results = queryable.Cast <Entity>().ChangeQueryType(currentType).ToList().Except(entitiesToDelete).ToList();
if (results.Count > 0)
{
constraints.AddRange(results.Select(x => $"Entity '{entityMetadata.Name}' with Id = '{x.Id}' references '{entityType.Name}' in {string.Join(", ", fields.Select(y => $"'{y.Name}'"))}."));
}
}
return(constraints);
}