The symbol size of Data Matrix ECC200 consists of even rows and even columns. Some symbols are square with sizes from 10*10 to 144*144; some symbols are rectangular with sizes from 8*18 to 16*48
Here is a sample code of create Data Matrix in .net.
using BusinessRefinery.Barcode;

DataMatrix barcode = new DataMatrix();
barcode.Code = "Data Matrix";
barcode.Format = ImageFormat.Gif;
barcode.drawBarcode2ImageFile("c:/data-matrix-csharp.gif");