i face an error by addind column into excel sheet. using SqlBulkCopy

See more:

C#

ASP.NET

public void BulkCopy(DataTable dt, string TableName)
        {

            var configurationAppSettings = new System.Configuration.AppSettingsReader();

            using (SqlBulkCopy sqlBulk = new SqlBulkCopy(((string)(configurationAppSettings.GetValue("ConnectionString", typeof(string))))))
            {
                sqlBulk.DestinationTableName = TableName;
                sqlBulk.BulkCopyTimeout = 3000;
                sqlBulk.WriteToServer(dt);
                sqlBulk.Close();

}}
this is bulk copy fuction i used i face an error when adding a column into excel sheet.. i face an error
:The given value of type String from the data source cannot be converted to type bigint of the specified target column
The code i used behind import button is that
Note.. All working fine before i adding a new column..
private bool ImportHours()
{
var result = false;
DataTable dt = new DataTable();
DataSet ds = new DataSet();

var RequiredColumns = new string[] { "SSN", "LASTNAME", "FIRSTNAME", "LEVEL1CODE", "LEVEL1DESCRIPTION", "LEVEL2CODE", "LEVEL2DESCRIPTION", "LEVEL3CODE", "LEVEL3DESCRIPTION", "LEVEL4CODE", "LEVEL4DESCRIPTION", "LEVEL5CODE", "LEVEL5DESCRIPTION", "DATEOFHIRE", "UNIONCODE", "PPE", "HOURS", "GROSSWAGES", "TERMINATIONDATE", "PAYFREQUENCY","STATUS"};

string filename = String.Format("{1}\\{2}{0}", Path.GetExtension(fuCsv.PostedFile.FileName), Server.MapPath("ImportFiles"), DateTime.Now.Ticks);

var strArray2 = new string[] { ".csv", ".xls", ".xlsx" };

if (objImport.ValidateFileExtention(filename, strArray2))
{
fuCsv.SaveAs(filename);

switch (Path.GetExtension(filename))
{

case ".xlsx":
ds = objImport.XlsxReader(filename);

break;
case ".csv":
dt = objImport.GetDataTabletFromCSVFile(filename);
dt.TrimColumnNames();
break;
}

QueryHelper.ExecuteNonQuery("DELETE FROM Tbl_PPACA_Import");
int i = 0, j = 0;
foreach (DataTable dT in ds.Tables)
{

if (dT.GetColumnNames().Length > 0)
{
i++;

dt = dT;
dt.TrimColumnNames();

var aa = string.Join(",", dt.DefaultView.ToTable(false, RequiredColumns).GetColumnNames());
var ab = string.Join(",", RequiredColumns);

if (aa == ab)
{
var Employer_ID = new System.Data.DataColumn("EmployerID", typeof(System.Int32)) { DefaultValue = EmployerID };
var PayrollActivityDateCol = new System.Data.DataColumn("PAYROLLACTIVITYDATE", typeof(System.DateTime)) { DefaultValue = PayrollActivityDate.SelectedDate };
var Change_IP = new DataColumn("ChangeIP") { DefaultValue = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"] };
var ModifiedBy = new DataColumn("ModifiedBy", typeof(string)) { DefaultValue = _userInfo.Name };
var UserType = new DataColumn("UserType", typeof(string)) { DefaultValue = _userInfo.UserTypeString };
var ModifiedDate = new DataColumn("ModifiedDate", typeof(DateTime)) { DefaultValue = DateTime.Now };


dt = new DataView(dt).ToTable(false, RequiredColumns);

dt = dt.Select(string.Format("Convert([SSN],'System.String') <> '{0}'", string.Empty)).CopyToDataTable();


foreach (DataRow row in dt.Rows)
{
if (!Methods.isDate(row["DATEOFHIRE"]))
row.SetField("DATEOFHIRE", null as System.DBNull);
if (!Methods.isDate(row["PPE"]))
row.SetField("PPE", null as System.DBNull);
if (!Methods.isDate(row["TERMINATIONDATE"]))
row.SetField("TERMINATIONDATE", null as System.DBNull);
if (!Methods.isDouble(row["HOURS"]))
row["HOURS"] = 0.00;
if (!Methods.isDouble(row["GROSSWAGES"]))
row["GROSSWAGES"] = 0.00;

}

dt.Columns.AddRange(new DataColumn[] { Employer_ID, PayrollActivityDateCol, Change_IP, ModifiedBy, UserType, ModifiedDate });

objImport.BulkCopy(dt, "Tbl_PPACA_Import");

j++;
}
}

}

if (i == j)
result = true;


}
else
{
Label1.ForeColor = System.Drawing.Color.Red;
Label1.Text = "Invalid File. Please upload a File with extension " + string.Join(",", strArray2);
result = false;
}

return result;
}