I've run into a bit of a problem, which I simply cannot find a good work-around to.
I want to have these 3 overloads:
public IList<T> GetList<T>(string query) where T: string
public IList<T> GetList<T>(string query) where T: SomeClass
public IList<T> GetList<T>(string query) where T: struct
Obviously the first constraint won't even compile alone, so that's my first issue. (I realise I could just make it IList but I want the same syntax for the three)
Anyway the reason for all this, is these methods are part of a wrapper around executing SQL queries against a database - I want to be able to return the result as a list of strings (in case someone selects a varchar column), a list of valuetypes (int, float, whatever) or a list of classes (these classes represent tables, and thus contains multiple columns)
I hope that part was somewhat understandable :-)
Anyway my big problem is obviously that I cannot make these overloads, since they use the same name and parameterlist.
Also I cannot merge them into the same method, since I need to call a method on SomeClass in that implementation, so unless I want to do some heavy typecasting, or worse, reflection - I need that constraint.
I realise that what I'm trying to do isn't possible, so what I'm searching for is a good approach, that'll mimic my intentions.
If some of this is a bit unclear, feel free to ask :-)
Edit:
Here's my current code for the "where T: SomeClass" version. I'm trying to add support for string/valuetypes to this current code, so maybe my initial approach is just plain wrong - any ideas are welcome basically :-)
public IList<TValue> GetList<TValue>(string query) where TValue : DbTable, new()
{
DataSet dataSet = GetDataSet(query);
IList<TValue> result = new List<TValue>();
if (dataSet.Tables.Count > 0)
{
foreach (DataRow row in dataSet.Tables[0].Rows)
{
TValue col = new TValue();
col.Fill(row);
result.Add(col);
}
}
return result;
}
As you can see I need the exact type of DbTable in order to new the proper constructor.
Fill is an abstract method of DbTable (which is an abstract class).
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