Relationships and Lazy Loading in SubSonic 3.0

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I'm playing around with SubSonic 3.0 at the moment, and it looks really straight-forward (except that I still have to decide between SimpleRepository and ActiveRecord, but that's another story).

However, as the documentation is a bit sparse, I am not sure if it supports foreign-relationships and lazy-loading. Essentially, I have a class posting:

public class Posting {
    [SubSonicPrimaryKey]
    public Guid InternalId { get; set; }
    public string Title { get; set; }
    public string Body { get; set; }
    public DateTime? PostingDate { get; set; }
    public List<Comment> Comments { get; set; }
}

and a class Comment:

public class Comment
{
    public string Body { get; set; }
}

As you see, Posting has a List of Comments. Can I somehow tell SubSonic that these two are related? That is that I can automatically save all Comments when I save the Post? And more importantly, when I load a Posting, I'd like the List of Comments to be empty at first, and at some point say "Okay, please populate it now".

I know I can manually manage this in Code, but I just like to know if SubSonic can do that before I do the manual work.

Best Answer

Sparse? Have you read them yet?

ActiveRecord can determine your relationships based on FKs (so can the Linq Templates) and will use IQueryable. So you get the best of both worlds - they're there if you need them.

If you use Simple Repo - no - this doesn't happen and it's all manual.

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – How to create an Excel (.XLS and .XLSX) file in C# without installing Microsoft Office

You can use a library called ExcelLibrary. It's a free, open source library posted on Google Code:

ExcelLibrary

This looks to be a port of the PHP ExcelWriter that you mentioned above. It will not write to the new .xlsx format yet, but they are working on adding that functionality in.

It's very simple, small and easy to use. Plus it has a DataSetHelper that lets you use DataSets and DataTables to easily work with Excel data.

ExcelLibrary seems to still only work for the older Excel format (.xls files), but may be adding support in the future for newer 2007/2010 formats.

You can also use EPPlus, which works only for Excel 2007/2010 format files (.xlsx files). There's also NPOI which works with both.

There are a few known bugs with each library as noted in the comments. In all, EPPlus seems to be the best choice as time goes on. It seems to be more actively updated and documented as well.

Also, as noted by @АртёмЦарионов below, EPPlus has support for Pivot Tables and ExcelLibrary may have some support (Pivot table issue in ExcelLibrary)

Here are a couple links for quick reference:
ExcelLibrary - GNU Lesser GPL
EPPlus - GNU (LGPL) - No longer maintained
EPPlus 5 - Polyform Noncommercial - Starting May 2020
NPOI - Apache License

Here some example code for ExcelLibrary:

Here is an example taking data from a database and creating a workbook from it. Note that the ExcelLibrary code is the single line at the bottom:

//Create the data set and table
DataSet ds = new DataSet("New_DataSet");
DataTable dt = new DataTable("New_DataTable");

//Set the locale for each
ds.Locale = System.Threading.Thread.CurrentThread.CurrentCulture;
dt.Locale = System.Threading.Thread.CurrentThread.CurrentCulture;

//Open a DB connection (in this example with OleDB)
OleDbConnection con = new OleDbConnection(dbConnectionString);
con.Open();

//Create a query and fill the data table with the data from the DB
string sql = "SELECT Whatever FROM MyDBTable;";
OleDbCommand cmd = new OleDbCommand(sql, con);
OleDbDataAdapter adptr = new OleDbDataAdapter();

adptr.SelectCommand = cmd;
adptr.Fill(dt);
con.Close();

//Add the table to the data set
ds.Tables.Add(dt);

//Here's the easy part. Create the Excel worksheet from the data set
ExcelLibrary.DataSetHelper.CreateWorkbook("MyExcelFile.xls", ds);

Creating the Excel file is as easy as that. You can also manually create Excel files, but the above functionality is what really impressed me.

Best Answer

Related Solutions

C# – the difference between String and string in C#

This is the style that Microsoft tends to use in their examples.

C# – How to create an Excel (.XLS and .XLSX) file in C# without installing Microsoft Office

Related Topic