How can I store an array of doubles to database using Entity Framework Code-First with no impact on the existing code and architecture design?
I've looked at Data Annotation and Fluent API, I've also considered converting the double array to a string of bytes and store that byte to the database in it own column.
I cannot access the public double[] Data { get; set; } property with Fluent API, the error message I then get is:
The type double[] must be a non-nullable value type in order to use
it as parameter 'T'.
The class where Data is stored is successfully stored in the database, and the relationships to this class. I'm only missing the Data column.
You can do a thing like this :
[NotMapped]
public double[] Data
{
get
{
string[] tab = this.InternalData.Split(',');
return new double[] { double.Parse(tab[0]), double.Parse(tab[1]) };
}
set
{
this.InternalData = string.Format("{0},{1}", value[0], value[1]);
}
}
[EditorBrowsable(EditorBrowsableState.Never)]
public string InternalData { get; set; }
Thank you all for your inputs, due to your help I was able to track down the best way to solve this. Which is:
public string InternalData { get; set; }
public double[] Data
{
get
{
return Array.ConvertAll(InternalData.Split(';'), Double.Parse);
}
set
{
_data = value;
InternalData = String.Join(";", _data.Select(p => p.ToString()).ToArray());
}
}
Thanks to these stackoverflow posts:
String to Doubles array and
Array of Doubles to a String
I know it is a bit expensive, but you could do this
class Primitive
{
public int PrimitiveId { get; set; }
public double Data { get; set; }
[Required]
public Reference ReferenceClass { get; set; }
}
// This is the class that requires an array of doubles
class Reference
{
// Other EF stuff
// EF-acceptable reference to an 'array' of doubles
public virtual List<Primitive> Data { get; set; }
}
This will now map a single entity (here 'Reference') to a 'list' of your Primitive class. This is basically to allow the SQL database to be happy, and allow you to use your list of data appropriately.
This may not suit your needs, but will be a way to make EF happy.
It would be far easier if you use List<double> rather then double[]. You already have a table that stores your Data values. You probably have foreign key from some table to the table where your double values are stored. Create another model that reflects the table where doubles are stored and add foreign key mappings in the mappings class. That way you will not need to add some complex background logic which retrieves or stores values in a class property.
In my opinion almost all other answers work on the opposite of how it should be.
Entity EF should manage the string and the array must be generated from it. So the array must be whole read and written only when the string is accessed by EF.
A solution involving logic on Data[] is wrong because, as I wrote in a comment, you would run into paradoxical conditions. In all other conditions the variable must remain a pure array.
By putting the "get" and "set" logic in Data[], as I've seen so far, this happens:
1 - Every time an index access is made to the array, the array is automatically recreated from the string. This is a useless work, think of an iteration in a loop...
2 - when you go to set a single element it is not stored because it passes through "get" and not "set".
If you try to declare Data=new []{0,0,0} then set Data[1]=2 , going to re-read Data[1] the result is 0.
My solution is to completely turn the logic around.
public string Data_string
{
get => string.Join(';', Data??Array.Empty());
set => Data= value == null ? Array.Empty<double>() : Array.ConvertAll(value.Split(';',StringSplitOptions.RemoveEmptyEntries), double.Parse);
}
[NotMapped]
public double[] Data {get;set;}
Obviously this only applies to storing and retrieving data on databases, access to Data_string is exclusive to EF.
Once the string is read from the DB it is associated to Data_string which, through set, creates the Data array.
At this point you can work on Data without affecting the string in any way, like a normal array.
When you will ask EF to save in the DB, through the get in the Data_string property, the string will be completely reconstructed based on the Data elements and then stored as a string.
Practically the string is modified only twice, at the moment of reading from the DB and at the moment of saving.
In my opinion this solution is much more efficient than operating continuously on the string.
Nathan White has the best answer (got my vote).
Here is a small improvement over Joffrey Kern's answer to allow lists of any length (untested):
[NotMapped]
public IEnumerable<double> Data
{
get
{
var tab = InternalData.Split(',');
return tab.Select(double.Parse).AsEnumerable();
}
set { InternalData = string.Join(",", value); }
}
[EditorBrowsable(EditorBrowsableState.Never)]
public string InternalData { get; set; }
Don't use double[] use List insted.
Like this.
public class MyModel{
...
public List<MyClass> Data { get; set; }
...
}
public class MyClass{
public int Id { get; set; }
public double Value { get; set; }
}
All that solution that I see there are bad, because:
If you create table, you don't want to store data like this: "99.5,89.65,78.5,15.5" that's not valid! Firstly its a string that means if you can type letter into it and at the moment when your ASP.NET server call double.Parse it will result in FormatException and that you really don't want!
It's slower, because your server must parse the string. Why parse the string instead getting almost ready data from SQL Server to use?
i know this post is Ancient, but in case someone still needs to do something like this, PLEASE DO NOT USE THE ABOVE SOLUTIONS,
as the above solutions are EXTREMELY inefficient (Performance and Disk Space wise).., the best way is to store the array as a Byte array
public byte[] ArrayData;
[NotMapped]
public double[] Array {
get {
var OutputArray = new double[ArrayData.Length / 8];
for (int i = 0;i < ArrayData.Length / 8;i++)
OutputArray[i] = BitConverter.ToDouble(ArrayData, i * 8);
return OutputArray;
}
set {
var OutputData = new byte[value.Length * 8];
for (int i = 0;i < value.Length;i++) {
var BinaryValue = BitConverter.GetBytes(value[i]);
OutputData[(i*8)] = BinaryValue[0];
OutputData[(i*8)+1] = BinaryValue[1];
OutputData[(i*8)+2] = BinaryValue[2];
OutputData[(i*8)+3] = BinaryValue[3];
OutputData[(i*8)+4] = BinaryValue[4];
OutputData[(i*8)+5] = BinaryValue[5];
OutputData[(i*8)+6] = BinaryValue[6];
OutputData[(i*8)+7] = BinaryValue[7];
}
ArrayData = OutputData;
}
}
`
And if you need more performance, you can go for Unsafe code and use pointers .. instead of BitConverter ..
This is way better than saving double values (that can get huge) as string, then spliting the string array !! and then parsing the strings to double !!!
These getter/setters work on the whole array, but if you need to get just one item from the array, you can make a function that gets a single item from the array with a complexity of O(1) :
for Get :
public double Array_GetValue(int Index) {
return BitConverter.ToDouble(ArrayData, Index * 8);
}
for Set :
public void Array_SetValue(int Index, double Value) {
var BinaryValue = BitConverter.GetBytes(Value);
ArrayData[(Index*8)] = BinaryValue[0];
ArrayData[(Index*8)+1] = BinaryValue[1];
ArrayData[(Index*8)+2] = BinaryValue[2];
ArrayData[(Index*8)+3] = BinaryValue[3];
ArrayData[(Index*8)+4] = BinaryValue[4];
ArrayData[(Index*8)+5] = BinaryValue[5];
ArrayData[(Index*8)+6] = BinaryValue[6];
ArrayData[(Index*8)+7] = BinaryValue[7];
}
If your collection can be null or empty, and you want this to be preserved, do this:
[NotMapped]
public double[] Data
{
get => InternalData != null ? Array.ConvertAll(Data.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries), double.Parse) : null;
set => InternalData = value != null ? string.Join(";", value) : null;
}
Also, specify [Column(TypeName = "varchar")] on the string property for a more efficient storage data type.
A perfect enhancement to #Jonas's answer will be to add the necessary annotations. So, a cleaner version would be
[EditorBrowsable(EditorBrowsableState.Never)]
[JsonIgnore]
public string InternalData { get; set; }
[NotMapped]
public double[] Data
{
get => Array.ConvertAll(InternalData.Split(';'), double.Parse);
set
{
InternalData = string.Join(";", value.Select(p => p.ToString(CultureInfo.InvariantCulture)).ToArray());
}
}
The [JsonIgnore] Annotation will ignore the InternalData field from JSON serialization and Swagger UI.
[EditorBrowsable(EditorBrowsableState.Never)] will hide the public method from the IDE IntelliSense
In app I'm bulding I used data model presented by James_D here:
Applying MVC With JavaFx
I just can find a way to bind labels text to property of object held in DataModel
Data is structured like this:
model class Student
//partial class
public class Student {
private final StringProperty displayName = new SimpleStringProperty();
public final StringProperty displayNameProperty(){
return this.displayName;
}
public Student(){
}
public final String getDisplayName() {
return this.displayNameProperty().get();
}
public final void setDisplayName(String displayName) {
this.displayNameProperty().set(displayName);
}
}
Student instaces are held by StudentDataModel class
public class StudentDataModel {
// complete student list
private final ObservableList<Student> studentList = FXCollections.observableArrayList();
private final ObjectProperty<Student> selectedStudent = new SimpleObjectProperty<>(new Student());
public final Student getSelectedStudent() {
return selectedStudent.get();
}
public final ObjectProperty<Student> selectedStudentProperty() {
return selectedStudent;
}
public final void setSelectedStudent(Student student) {
selectedStudent.set(student);
}
}
StudentList is displayed by Table View, there is change listener that sets selectedStudent like this:
public class TableViewController {
public void initModel(StudentDataModel studentDM) {
// ensure model is set once
if (this.studentDM != null) {
throw new IllegalStateException("StudentDataModel can only be initialized once");
}
this.studentDM = studentDM;
tableView.getSelectionModel().selectedItemProperty().addListener((obs, oldSelection, newSelection) -> {
if (newSelection != null) {
studentDM.setSelectedStudent(newSelection);
}
});
}}
There is another controller ActionsBarController that has label to display selected student (this seems redundant, but there is option for selecting multiple objects to perform bulk operations).
StudentDataModel is initialized properly (I can see it in debuger) but below doesn't do anything:
chosenStudentLabel.textProperty().bind(studentDM.getSelectedStudent().displayNameProperty());
//this shows class name with instance number changing correctly
chosenStudentLabel.textProperty().bind(studentDM.selectedStudentProperty().asString());
I could inject ActionsBarController to TableViewController and change label text from change Listener there, but this seems counter productive with data model.
What am I doing wrong?
Your code doesn't work, because you call (and evaluate) getSelectedStudent() at the time the binding is created (i.e. when you initialize the model). As a consequence, you only bind to the displayName property of the student that is selected at that time. (If nothing is selected, you'll get a NullPointerException.) The binding will only change if that initially-selected student's display name changes; it won't change if the selection changes.
You need a binding that unbinds from the old selected student's display name, and binds to the new selected student's display name, when the selected student changes. One way to do this is:
chosenStudentLabel.textProperty().bind(new StringBinding() {
{
studentDM.selectedStudentProperty().addListener((obs, oldStudent, newStudent) -> {
if (oldStudent != null) {
unbind(oldStudent.displayNameProperty());
}
if (newStudent != null) {
bind(newStudent.displayNameProperty());
}
invalidate();
});
}
#Override
protected String computeValue() {
if (studentDM.getSelectedStudent() == null) {
return "" ;
}
return studentDM.getSelectedStudent().getDisplayName();
}
});
Note that there is also a "built-in" way to do this, but it's a bit unsatisfactory (in my opinion) for a couple of reasons. Firstly, it relies on specifying the name of the "nested property" as a String, using reflection to access it. This is undesirable because it has no way to check the property exists at compile time, it requires opening the module for access, and it is less good performance-wise. Secondly, it gives spurious warnings if one of the properties in the "chain" is null (e.g. in this case if the selected student is null, which is will be initially), even though this is a supported case according to the documentation. However, it is significantly less code:
chosenStudentLabel.textProperty().bind(
Bindings.selectString(studentDM.selectedStudentProperty(), "displayName")
);
I am trying to bind an ObservableCollection, which is filled in a Background thread, to a charting Control in the UI.
Therefore i have a static class "Core", which have a member "DataState". This DataState class owns the ObservableCollection "SensorData", which is filled in the aforementioned Background Task.
As there is no possibility to do UWP XAML Binding for static properties i wrote a wrapper class "DataWrapper" which is nonstatic and refers to the static Core.DataState.SensorData-object.
Here's some of my Code:
Core.cs:
public static partial class Core
{
private static DataState m_DataState;
public static DataState DataState
{
get
{
return m_DataState;
}
set
{
if (value != null)
{
m_DataState = value;
}
}
}
}
DataState.cs:
public class DataState
{
private ObservableCollection<SensorData> m_SensorData = new ObservableCollection<SensorData>();
public ObservableCollection<SensorData> SensorData
{
get
{
return m_SensorData;
}
set
{
if (value != null)
m_SensorData = value;
}
}
DataWrapper.cs:
public class DataWrapper
{
public ObservableCollection<SensorData> SensorData
{
get
{
return Core.DataState.SensorData;
}
}
}
XAML:
<Charting:LineSeries Name="MySeries" Title="Title" IndependentValuePath="X" DependentValuePath="Y" ItemsSource="{x:Bind DataWrapper.SensorData}"></Charting:LineSeries>
where X and Y are the variables contained in the SensorData-Object.
So, if i wait to Show the Charting-Control until there's some data in the ObservableCollection this data is nicely plotted into my Control. But after that recently added data is not plotted anymore.
Therefore i am looking for a way to route the PropertyChanged-Event from Core.DataState.SensorData somehow to DataWrapper.SensorData. Is there any possibility to do this?
Is the structure of this Problem clear to you? I think my descriptions sounds a bit confusing...
Thank you in advance for any help :-)
When I try to index a doc of my defined type, having a list which is supposed to be mapped as a nested-object ("type":"nested"), it's getting mapped as a regular object type.
Take a look at the code:
I've got a simple class like this one:
[ElasticType()]
public class MyJob
{
[ValueFieldAttribute]
public int jobCode { get; set; }
[ValueFieldAttribute(Type = FieldType.nested)]
public IList<JobProfessionalFieldInfo> JobProfessionalFields { get; set; }
}
The code for the JobProfessionalFieldInfo class is:
[ElasticType()]
public class JobProfessionalFieldInfo
{
[ValueFieldAttribute]
public int JobId { get; set; }
[ValueFieldAttribute]
public int CategoryId { get; set; }
}
The code for the ValueFieldAttribute class is:
public class ValueFieldAttribute : ElasticPropertyAttribute
{
public ValueFieldAttribute()
: base()
{
this.Store = false;
this.Index = FieldIndexOption.not_analyzed;
}
}
My program:
static void Main(string[] args)
{
ConnectionSettings node = new ConnectionSettings(new Uri("http://localhost:9200"));
node.SetDefaultIndex("jobs");
ElasticClient client = new ElasticClient(node);
List<JobProfessionalFieldInfo> list = new List<JobProfessionalFieldInfo>();
list.Add(new JobProfessionalFieldInfo { CategoryId = 1, JobId = 1 });
list.Add(new JobProfessionalFieldInfo { CategoryId = 2, JobId = 2 });
var res = client.Index<MyJob>(new MyJob
{
jobCode = 1,
JobProfessionalFields = list
},"jobs", "MyJob",1);
}
Now, when I run it, it indexes the object successfully... BUT(!!) when I get the mapping of the index with GET jobs/MyJob/_mapping, I see that jobProfessionalFields has no "type":"nested" in its mapping.
That results in a query like the following one, returning the indexed doc while it's not supposed to get it back (that's what nested-type is for right?..):
GET jobs/_search
{
"query":
{
"bool":
{
"must":
[
{"match": {"jobId":1}},
{"match": {"categoryId":2}}
]
}
}
}
It's not the end:
I'd a look at here,
there the guy that answered tells that when we use annotations we need to manually call the createIndex and Map methods, but the problem is that I don't have any generic Map method...!
Take a look at here: (just to make you get into the link - here's its start..)
namespace Nest
{
public partial class ElasticClient...
And I don't know how to use the non-generic Map method to put the mapping of my MyJob class.
How can I cause this stuff to map the jobProfessionalFields as nested-type dudes?
Thanks for any help of you guys!
OK, got it LOL!
The MapFromAttributes<> is the right generic method for putting the mapping (at least in the current Nest version I'm using - 0.12.0).
But it demands a manual call for the index creationg, o.w it gives an IndexMissing exception (like the guy in the above mentioned link said).
client.CreateIndex("jobs", new IndexSettings { });
var res = client.MapFromAttributes<MyJob>("jobs","MyJob");
But that's really interesting why isn't it enough to just define the
[ElasticProperty(Type = FieldType.nested)],
in order to get the nested mapping though..
I would be glad to get an answer for that one.
Any idea how to do what the title says? Only thing I found was on the original Velocity site, and I don't think
ve.setProperty( RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS,
"org.apache.velocity.runtime.log.Log4JLogChute" );
ve.setProperty("runtime.log.logsystem.log4j.logger",
LOGGER_NAME);
will work wonderfully well on .NET. I am using log4net, which should make it quite easy, but the documentation on NVelocity is really a mess.
Implement NVelocity.Runtime.Log.ILogSystem (you could write a simple implementation that bridges to log4net) and set this impl type in the property RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS
How I got this information:
Get the code.
Search for "log" in the codebase
Discover the classes in NVelocity.Runtime.Log.
Read those classes' source, they're very simple and thoroughly documented.
Update:
Currently, NVelocity does not support logging. The initializeLogger() and Log() methods in RuntimeInstance Class are commented out.
If you need to log, uncomment the two methods, add a private ILogSystem logSystem; property
Here's our on-the-fly implementation:
public class RuntimeInstance : IRuntimeServices
{
private ILogSystem logSystem;
...
...
private void initializeLogger()
{
logSystem = LogManager.CreateLogSystem(this);
}
...
...
private void Log(LogLevel level, Object message)
{
String output = message.ToString();
logSystem.LogVelocityMessage(level, output);
}
...
}
Then, we implemented ILogSystem for log4net
using log4net;
using NVelocity.Runtime;
using NVelocity.Runtime.Log;
namespace Services.Templates
{
public class Log4NetILogSystem : ILogSystem
{
private readonly ILog _log;
public Log4NetILogSystem(ILog log )
{
_log = log;
}
public void Init(IRuntimeServices rs)
{
}
public void LogVelocityMessage(LogLevel level, string message)
{
switch (level)
{
case LogLevel.Debug:
_log.Debug(message);
break;
case LogLevel.Info:
_log.Info(message);
break;
case LogLevel.Warn:
_log.Warn(message);
break;
case LogLevel.Error:
_log.Error(message);
break;
}
}
}
}
Then, when creating the engine:
var engine = new VelocityEngine();
var props = new ExtendedProperties();
props.SetProperty(RuntimeConstants.RUNTIME_LOG_LOGSYSTEM,
new Log4NetILogSystem(LogManager.GetLogger(typeof(NVelocityEngine))));
engine.Init(props);