How to merge Multiple datatable in a single datatable

not working as expected.. here am getting only 3 columns.I dont need to remove duplicates.below am trying
 
var Dset = new DataSet();
DataTable dt1 = new DataTable();
dt1.Columns.Add("Name", typeof(string));
dt1.Columns.Add("Age", typeof(int));
// Create a DataRow, add Name and Age data, and add to the DataTable
DataRow dr1 = dt1.NewRow();
dr1["Name"] = "Mohammadsd"; // or dr[0]="Mohammad";
dr1["Age"] = 24; // or dr[1]=24;
dt1.Rows.Add(dr1);
Dset.Tables.Add(dt1);
DataTable dt2 = new DataTable();
dt2.Columns.Add("Name", typeof(string));
dt2.Columns.Add("Age", typeof(int));
// Create a DataRow, add Name and Age data, and add to the DataTable
DataRow dr2 = dt2.NewRow();
dr2["Name"] = "Mohammad"; // or dr[0]="Mohammad";
dr2["Age"] = 24; // or dr[1]=24;
dt2.Rows.Add(dr2);
Dset.Tables.Add(dt2);
DataTable dt3 = new DataTable();
dt3.Columns.Add("Name", typeof(string));
dt3.Columns.Add("sex", typeof(int));
// Create a DataRow, add Name and Age data, and add to the DataTable
DataRow dr3 = dt3.NewRow();
dr3["Name"] = "last"; // or dr[0]="Mohammad";
dr3["sex"] = 24; // or dr[1]=24;
dt3.Rows.Add(dr3);
Dset.Tables.Add(dt3);
DataTable dtFinal = new DataTable("dtEmployee");
for (int i = 0; i < Dset.Tables.Count; i++)
{
dtFinal.Merge(Dset.Tables[i]);
}
var ds = new DataSet();
ds.Tables.Add(dtFinal);//here i need to get 6 colms

You need to Call the Copy() method in each iteration if you want to preserve the table

DataTable dtFinal = new DataTable();  
  
            for (int i = 0; i < resultDS.Tables.Count; i++)  
  
            {  
  
                    dtFinal = resultDS.Tables[i].Copy();  
                    dtFinal.Merge(resultDs.Tables[i]);  
  
            }  
            var ds = new DataSet();  
  
            ds.Tables.Add(dtFinal);