Datasets to Dictionary Join?

Check if the following is useful to you:
I am adding two data tables here. In your case get datatable from datasets as below.
DataTable dt1 = ds1.Tables[0];
DataTable dt2 = ds2.Tables[0];

//My Example
DataTable dt1=new DataTable("table1");
dt1.Columns.Add("CompanyName", typeof(string));
dt1.Columns.Add("Address", typeof(string));

DataTable dt2 = new DataTable("table2");
dt2.Columns.Add("CompanyName" typeof(string));
dt2.Columns.Add("CompanyID", typeof(string));
//Adding sample data
dt1.Rows.Add("Company1","Address1");
dt1.Rows.Add("Company2","Address2");

dt2.Rows.Add("Company1","ID1");
dt2.Rows.Add("Company3","ID3");

Now we want to get rows with criteria that company name matches in two tables. Use LINQ query and get the results:

var result = from table1 in dt1.AsEnumerable()
                join table2 in dt2.AsEnumerable()
                on (string) table1["CompanyName"] equals (string) table2["CompanyName"]
                select new
                {        
                        Name = (string)table1["CompanyName"],
                        Address=(string)table1["Address"],
                        CompanyID=(string)table2["CompanyID"]
                };
Now get the data (Matching rows):
foreach(var obj in result)
{
        string CompanyName = obj.Name;
        string Address = obj.Address;
        string ID = obj.CompanyID;
}
        
Here we see matching company name is Company1 and so you should get only one resultset.