I get an error when creating a datarelation - 'DataRelation does not contain a constuctor that takes 3 arguments. Where am I going wrong.

```
DataColumn dcParent = ds.Tables["Directors"].Columns["did"];
DataColumn dcChild = ds.Tables["Movies"].Columns["did"];

//Error here
DataRelation MovieDirectors = new DataRelation("dr1", dcParent, dcChild);

```