Only one member on a type can capture the return value of a command; remove the duplicate.

Bad:

[DbValue(Direction = ParameterDirection.ReturnVaue)]
public int X {get;set;}

[DbValue(Direction = ParameterDirection.ReturnVaue)]
public int Y {get;set;}

Good:

[DbValue(Direction = ParameterDirection.ReturnVaue)]
public int X {get;set;}

public int Y {get;set;}