Master - Detail example

Here is one my example of in-memory DataTables master - detail relationship.
Create table with code like:

DataTable dtMaster = new DataTable("Master");

In this example I will add Columns without specifying type:

dtMaster.Columns.Add("Id");

Create new row:

DataRow drMaster = dtMaster.NewRow();
drMaster["Id"] = 1;

Add row to DataTable:

dtMaster.Rows.Add(drMaster);

Now details table:

DataTable dtDetail = new DataTable("Details");
dtDetail.Columns.Add("Id");
dtDetail.Columns.Add("FkDetailMasterId");

DataRow drDetail = dtDetail.NewRow();
drDetail["Id"] = 1;
drDetail["FkDetailMasterId"] = 1;
dtDetail.Rows.Add(drDetail);

Create DataSet and add relation:

DataSet ds = new DataSet();

ds.Tables.Add(dtMaster);
ds.Tables.Add(dtDetail);

DataRelation relMasterDetail = new DataRelation("MyRelation"
	, ds.Tables["Master"].Columns["Id"]
	, ds.Tables["Details"].Columns["FkDetailMasterId"]
);

ds.Relations.Add(relMasterDetail);

Example download from here.