How to read XML File in a WCF Service ?

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C#

ASP.NET

WCF

Hello Friends,
I've this WCF Service where I need to Read Some data from an XML file & then I need to return that data to Client as string.
But I'm facing problem to Read the XML File in WCF Service Project.

Here is the code I used to Read & return the values:

IProduct.cs

[ServiceContract]
public interface IProduct
{
    [OperationContract]
    string GetID(int rno);

    [OperationContract]
    string GetName(int rno);

    [OperationContract]
    string GetDesc(int rno);

}

Product.cs

public class Product : IProduct
{

    public string GetID(int rno)
    {
        DataSet ds = new DataSet();
        try
        {
            ds.ReadXml("~/Products.xml");
            string res = ds.Tables[0].Rows[rno][0].ToString();
            return res;
        }
        catch
        {
            return "No More Data";
        }
    }

    public string GetName(int rno)
    {
        DataSet ds = new DataSet();
        try
        {
            ds.ReadXml("Products.xml");
            string res = ds.Tables[0].Rows[rno][0].ToString();
            return res;
        }
        catch
        {
            return "No More Data";
        }
    }

    public string GetDesc(int rno)
    {
        DataSet ds = new DataSet();
        try
        {
            ds.ReadXml("Products.xml");
            string res = ds.Tables[0].Rows[rno][0].ToString();
            return res;
        }
        catch
        {
            return "No More Data";
        }
    }
}

Now Friends plz Suggest me how can I read this XML File & return the data to Client ?

Thanks in Advance.
Regards,
Dash