ASP.NET

protected void AddEmptyColumnsToDatatable(DataTable datatable)
       {
           if (!datatable.Columns.Contains("HeadOfHousehold"))
           {
               DataColumn HeadOfHousehold = new DataColumn("HeadOfHousehold", Type.GetType("System.Boolean"));
               datatable.Columns.Add(HeadOfHousehold);
           }
           if (!datatable.Columns.Contains("Age"))
           {
               DataColumn Age = new DataColumn("Age", Type.GetType("System.Int32"));
               datatable.Columns.Add(Age);
           }
           if (!datatable.Columns.Contains("DateOfBirth"))
           {
               DataColumn DateOfBirth = new DataColumn("DateOfBirth", Type.GetType("System.String"));
               datatable.Columns.Add(DateOfBirth);
           }
           if (!datatable.Columns.Contains("Firstname"))
           {
               DataColumn DateOfBirth = new DataColumn("Firstname", Type.GetType("System.String"));
               datatable.Columns.Add(DateOfBirth);
           }
           if (!datatable.Columns.Contains("Lastname"))
           {
               DataColumn DateOfBirth = new DataColumn("Lastname", Type.GetType("System.String"));
               datatable.Columns.Add(DateOfBirth);
           }
           if (!datatable.Columns.Contains("SSN"))
           {
               DataColumn DateOfBirth = new DataColumn("SSN", Type.GetType("System.String"));
               datatable.Columns.Add(DateOfBirth);
           }
           if (!datatable.Columns.Contains("DOB"))
           {
               DataColumn DateOfBirth = new DataColumn("DOB", Type.GetType("System.String"));
               datatable.Columns.Add(DateOfBirth);
           }
           if (!datatable.Columns.Contains("AdultChild"))
           {
               DataColumn DateOfBirth = new DataColumn("AdultChild", Type.GetType("System.String"));
               datatable.Columns.Add(DateOfBirth);
           }
           if (!datatable.Columns.Contains("MaleFemale"))
           {
               DataColumn DateOfBirth = new DataColumn("MaleFemale", Type.GetType("System.String"));
               datatable.Columns.Add(DateOfBirth);
           }
           if (!datatable.Columns.Contains("ConsentForm"))
           {
               DataColumn DateOfBirth = new DataColumn("ConsentForm", Type.GetType("System.Boolean"));
               datatable.Columns.Add(DateOfBirth);
           }
           if (!datatable.Columns.Contains("Ethnicity"))
           {
               DataColumn DateOfBirth = new DataColumn("Ethnicity", Type.GetType("System.String"));
               datatable.Columns.Add(DateOfBirth);
           }

       }

//First I added these two lines to a function inside my load event, and the function only ran if the page wasn't a postback:
NewHouseholdDatatable = new DataTable();
                AddEmptyColumnsToDatatable(NewHouseholdDatatable);

protected void AddNewFamilyMemberToDatatable(string SSN, string First, string Last, string DOB, string AdultChild, string Gender, bool Head, String ConsentForm, string Ethnicity)
       {
         //If there was something in the viewstate, I loaded it from memory.  Otherwise, I simply recreated the table.
               if (ViewState["NewHouseholdDatatable"] != null)
               {
                   NewHouseholdDatatable = (DataTable)ViewState["NewHouseholdDatatable"];
                   //  FamilyWarning.Text += "<br/>There are now" + NewHouseholdDatatable.Rows.Count.ToString() + " rows in the table before adding empty columns and after getting changes";
                   AddEmptyColumnsToDatatable(NewHouseholdDatatable);//This is used to add empty columns to the datatable in case they aren't there already, otherwise I'd get a "does not contain column _ exception.
               }
               else
               {
                   NewHouseholdDatatable = new DataTable();
                   AddEmptyColumnsToDatatable(NewHouseholdDatatable);
               }
               FamilyWarning.Text += "<br/>There are now" + NewHouseholdDatatable.Rows.Count.ToString() + " rows in the table after adding empty columsn";

               FamilyWarning.Text += "<br/>There are now" + NewHouseholdDatatable.Rows.Count.ToString() + " rows in the table after assigning datasource";

               //NewHouseholdDatable is the name of the datatable I'm using, and it's set up in the page's Init event.
               DataRow Row = NewHouseholdDatatable.NewRow();
               //This stuff simply sets the values to the new row
               if (Head)
               {
                   Row["HeadOfHousehold"] = true;
               }
               else
               {
                   Row["HeadOfHousehold"] = false;

               }
               Row["Firstname"] = First;
               Row["DOB"] = DOB;
               Row["Lastname"] = Last;
               Row["SSN"] = SSN;
               Row["AdultChild"] = AdultChild;
               Row["MaleFemale"] = Gender;

               if (ConsentForm == "1")
               { Row["ConsentForm"] = true; }
               else
               { Row["ConsentForm"] = false; }
               Row["Ethnicity"] = Ethnicity;
               if (!CheckIsDate(DOB))
               {
                   Row["Age"] = 0;
                   Row["DateOfBirth"] = "Unknown, please edit and enter proper data";
               }
               else
               {
                   Row["Age"] = GetAge(DateTime.Parse(DOB));
                   DateTime DateAndTimeOfBirth = Convert.ToDateTime(DOB);
                   Row["DateOfBirth"] = DateAndTimeOfBirth.ToShortDateString();
               }
               try
               {
                   FamilyWarning.Text += "<br/>There are " + NewHouseholdDatatable.Rows.Count.ToString() + " rows in the table before adding";
                   NewHouseholdDatatable.Rows.Add(Row);


                   FamilyWarning.Text += "<br/>There are now" + NewHouseholdDatatable.Rows.Count.ToString() + " rows in the table after accepting changes";
                   ClearForm();
                   //FamilyMembers is the name of the gridview that I'm binding it to.,
                   ViewState["NewHouseholdDatatable"] = NewHouseholdDatatable;
                   FamilyMembers.DataSource = NewHouseholdDatatable;
                   FamilyMembers.DataBind();
                   FamilyWarning.Text += "<br/>There are now" + NewHouseholdDatatable.Rows.Count.ToString() + " rows in the table after databinding";
                   // FamilyWarning.Text = Row["Firstname"] + " " + Row["Lastname"] + " successfully added.  There are " + NewHouseholdDatatable.Rows.Count.ToString() + " rows in the table.";

               }
               catch (Exception ex)
               {
                   FamilyWarning.Text += "<br/>Unable to add this person to the table, " + ex.Message;
               }


       }

string cert_path = @"C:\cert.cer";
web_service.ClientCertificates.Add(X509Certificate.CreateFromCertFile(cert_path));