C# – Extract from DataRow or DataReader with one function

cdatareaderdatarownetsql

I'm looking for a solution for how to be able to extract data from a database when using either a DataRow and a DataReader with only one function (or one base function).

My problem stems from the fact that sometimes I need a DataReader and sometimes I need a DataTable/DataRow but then in order to extract the data from those objects I need two seperate Data access methods because they do not share an interface.

Basically when my database structure changes, I don't want to have to go in and write the following data retrieval code in multiple functions:

someValue = dr["someValue"]

It's the same syntax and does the same thing so I want a function that shares that functionality regardless of whether I'm using a DataReader or DataTable/DataRow to extract the data from the database.

Best Answer

You can use CreateDataReader method in DataTable class to access data through DbDataReader base class. Hence you can change the implementation but keep the mapping.

public List<MyType> GetMyTypeCollection(DbDataReader reader)
{
//mapping code here
}

It would be better if you can move to an ORM where you do not have to map manually.

Take a look at this micro ORM Dapper

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public static string AssemblyDirectory
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The Assembly.Location property sometimes gives you some funny results when using NUnit (where assemblies run from a temporary folder), so I prefer to use CodeBase which gives you the path in URI format, then UriBuild.UnescapeDataString removes the File:// at the beginning, and GetDirectoryName changes it to the normal windows format.

C# – Merging two arrays in .NET

In C# 3.0 you can use LINQ's Concat method to accomplish this easily:

int[] front = { 1, 2, 3, 4 };
int[] back = { 5, 6, 7, 8 };
int[] combined = front.Concat(back).ToArray();

In C# 2.0 you don't have such a direct way, but Array.Copy is probably the best solution:

int[] front = { 1, 2, 3, 4 };
int[] back = { 5, 6, 7, 8 };

int[] combined = new int[front.Length + back.Length];
Array.Copy(front, combined, front.Length);
Array.Copy(back, 0, combined, front.Length, back.Length);

This could easily be used to implement your own version of Concat.

Best Answer

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