June 2015 – Code musings in C#

It’s always a pain to work with DataTables and DataSets. You’re always typing these pesky column names, it doesn’t necessarily represents the actual data model (if there are nested data), there is no type safety until runtime, it’s pretty hard to use Linq on your results… the list goes on.

Fortunately, there is a simple solution: AutoMapper. It’s very simple to cast a DataTable to a list of objects:

public class Person {
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
}

List<Person> people = AutoMapper.Mapper.DynamicMap<IDataReader, List<Person>>(
    sourceDataTable.CreateDataReader());

public class Person {

public int Id { get; set; }

public string Name { get; set; }

public int Age { get; set; }

}

List<Person> people = AutoMapper.Mapper.DynamicMap<IDataReader, List<Person>>(

sourceDataTable.CreateDataReader());

I’m working on a pretty old application with no unit tests whatsoever, and I’m trying to write some as I add features and fix bugs.

After successively finding out about MS Fakes, then that it’s only included in VS2012+ Premium/Ultimate and very hard to include in a continuous integration chain, I was pretty stumped until I found this, which works incredibly well.

Another option to transform the static method into a static Func or Action. For instance.

Original code:

C#

class Math { public static int Add(int x, int y) { return x + y; } }

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class Math
{
    public static int Add(int x, int y)
    {
        return x + y;
    }
}

You want to “mock” the Add method, but you can’t. Change the above code to this:

C#

public static Func<int, int, int> Add = (x, y) => { return x + y; };

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public static Func<int, int, int> Add = (x, y) =>
{
    return x + y;
};

Existing client code doesn’t have to change (maybe recompile), but source stays the same.

Now, from the unit-test, to change the behavior of the method, just reassign an in-line function to it:

C#

[TestMethod] public static void MyTest() { Math.Add = (x, y) => { return 11; }; }

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[TestMethod]
public static void MyTest()
{
    Math.Add = (x, y) =>
    {
        return 11;
    };
}

Put whatever logic you want in the method, or just return some hard-coded value, depending on what you’re trying to do.

This may not necessarily be something you can do each time, but in practice, I found this technique works just fine.

Month: June 2015

Mapping DataTables to domain objects

Mocking static methods