how to delete or remove only text files from share point in C# or SSIS script?

// script code for downloading attachments from share point as well as remove attachments of particular files (like only .txt files , or only .csv .. etc)
public void Main()
{
try
{
//SPSecurity.RunWithElevatedPrivileges(delegate()
//{
String myFileExtension = "";
using (SPSite oSite = new SPSite("http://servername/sharepointname/"))
{
using (SPWeb oWeb = oSite.OpenWeb())
{
SPList list = oWeb.Lists["listName"];

SPListItemCollection oItemCol = list.GetItems();
foreach (SPListItem oItem in oItemCol)
{
string strID = Convert.ToString(oItem["ID"]);
SPFolder folder = oWeb.Folders["Lists"].SubFolders["ListName"].SubFolders["Attachments"].SubFolders[strID];
foreach (SPFile file in folder.Files)
{
FileInfo myFileinfo = new FileInfo(file.Name);
myFileExtension = myFileinfo.Extension.ToLower();
//MessageBox.Show("myFileExtension:" + myFileExtension);
String sFileextension = (Dts.Variables["fileformat"].Value.ToString().Trim()).ToLower();
if (myFileExtension.Equals(sFileextension))
{
WebClient client1 = new WebClient();
client1.Credentials = System.Net.CredentialCache.DefaultCredentials;
FileStream outStream = new FileStream(@"C:\\destination_folder\" + file.Name, FileMode.Create);
byte[] fileData = file.OpenBinary();
outStream.Write(fileData, 0, fileData.Count());
outStream.Close();
oItem.Attachments.Delete(file.Name);
oItem.Update();
}

}
}
}
}
//});
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
Dts.TaskResult = (int)ScriptResults.Success;
}
}


// only administrator can executes this code, bcz sharepoint list and attachments are assigned to different users, as user , user can't download all attachments from share point.