How do you create a custom datasource

Comments

• AlexTZ

  February 2009 edited 7:57PM

  Hello Luis,
  
  Please confirm if I understood you correctly:
  - you work with business objects
  - you register a business object by report.RegisterData(IEnumerable data, string name, BOConverterFlags flags, int maxNestingLevel) method
  - you need to create master-detail report, and you want to load detail datasource on demand
• lol

  February 2009 edited 7:57PM

  Hi, Alex
  
  That is correct.
  
  My domain is time and attendance, so let's say I have :
  
  1) A employee list
  2) Each employee has a schedule list
  3) I want to be able to report both on Employee and Employee.Schedules
  4) The schedule list must be generated and bound to the detail band (or datasource) just before needed and discarded afterwards.
  
  The reason as I stated previously is preserving resources.
  
  Thanks.
  
• AlexTZ

  February 2009 edited 7:57PM

  Ok, I've added the LoadBusinessObject event to the BusinessObjectDataSource. It will be available in the next build.
  
  Here is an example of how to use it (it's based on categories/products business object that is used in the demo):
  

  // make categories list and register it
        List<Category> list = new List<Category>();
        list.Add(new Category("Beverages", "Soft drinks, coffees, teas, beers"));
        list.Add(new Category("Confections", "Desserts, candies, and sweet breads"));
        list.Add(new Category("Seafood", "Seaweed and fish"));
        FReport.RegisterData(list, "Categories BusinessObject", BOConverterFlags.AllowFields, 3);
        
  // find the Products datasource and attach an event to it
        BusinessObjectDataSource ds = FReport.GetDataSource("Categories BusinessObject.Products") as BusinessObjectDataSource;
        if (ds != null)
          ds.LoadBusinessObject += new LoadBusinessObjectEventHandler(ds_LoadBusinessObject);
  
      private void ds_LoadBusinessObject(object sender, LoadBusinessObjectEventArgs e)
      {
  // e.Parent is Category instance, load its Products list
        Category category = e.Parent as Category;
        category.Products.Clear();
  
        switch (category.Name)
        {
          case "Beverages":
            category.Products.Add(new Product("Chai", 18m));
            category.Products.Add(new Product("Chang", 19m));
            category.Products.Add(new Product("Ipoh coffee", 46m));
            break;
  
          case "Confections":
            category.Products.Add(new Product("Chocolade", 12.75m));
            category.Products.Add(new Product("Scottish Longbreads", 12.5m));
            category.Products.Add(new Product("Tarte au sucre", 49.3m));
            break;
  
          case "Seafood":
            category.Products.Add(new Product("Boston Crab Meat", 18.4m));
            category.Products.Add(new Product("Red caviar", 15m));
            break;
        }
      }
  

  
  As you can see, there is no event like "UnloadData". It's because FastReport does not know exactly when the data is no longer needed. So you need to unload previous data in the same LoadBusinessObject event. Something like this:
  

      private Category FLastCategory;
  
      private void ds_LoadBusinessObject(object sender, LoadBusinessObjectEventArgs e)
      {
  // e.Parent is Category instance, load its Products list
        Category category = e.Parent as Category;
        category.Products.Clear();
  
        if (FLastCategory != null)
          FLastCategory.Products.Clear();
        FLastCategory = category;
  ...
  
• lol

  February 2009 edited 7:57PM

  Thank you,
  
  Looks good.
  
  I'll test it as soon as it's available and I'll you know my findings.
  
• lol

  March 2009 edited 7:57PM

  The event worked very well, I tried it to a depth of two descendants (master-detail-subdetail) and everything is fine.
  
  Thank you.
  
  Luis