How Do I Override Existing Rows Of Datatable With New Rows Coming From Imported Files If Primary Key Field Value Is Same?

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C#

C#4.0

I am working on a project and got small confusion. hope you can help me! I have one table that takes input from imported files. But when same file is again fetched from folder and about to save in table with changes in some field values it gives error ""violation of Primary key"" i solved it by using Ignore_Dup_key but after that it cannot saves the incoming row it just ignore that row.

ex : 1st file ==> 1,a,b,101
1st file again with different data ==> 1,f,d,102 where first field have primary key.

help me how can i solve this issue.

Here is code so far...

public void ImportAllFilesOfFolder()//function declares methods to import// 
{ 
   try { 
    SqlConnection con = new SqlConnection(@"--constr---");
    string sourceDir = @"---  folderPath---";
    var IcsvFile = Directory.EnumerateFiles(sourceDir, "*.csv");

            foreach (string currentFile in IcsvFile)
            {
                StreamReader sr = new StreamReader(currentFile);
                string line = sr.ReadLine();
                string[] value = line.Split(',');
                DataTable dt = new DataTable();
                DataRow row;

                foreach (string dc in value)
                {
                    dt.Columns.Add(new DataColumn(dc));
                }

                while (!sr.EndOfStream)
                {
                    value = sr.ReadLine().Split(',');
                    if (value.Length == dt.Columns.Count)
                    {
                        row = dt.NewRow();
                        row.ItemArray = value;
                        dt.Rows.Add(row);
                    }
                }
                string q = "ALTER TABLE DeviceDetails REBUILD WITH (IGNORE_DUP_KEY=ON)";
                SqlCommand cm = new SqlCommand(q, con);
                con.Open();
                cm.ExecuteNonQuery();
                con.Close();

                SqlBulkCopy bc = new SqlBulkCopy(con.ConnectionString, SqlBulkCopyOptions.TableLock);
                bc.DestinationTableName = "DeviceDetails";
                bc.BatchSize = dt.Rows.Count;
                con.Open();
                bc.WriteToServer(dt);
                bc.Close();
                con.Close();                  
            }