C# IF statement against SQLite query result

Question

I have a C# application that I am attempting to check my sqlite db if a filename already exists in the FileName column, if it DOESN'T exist, execute some code.. Here is what I am working with. To clarify - This code doesnt work.. it says I cannot convert insertCommand.ExecuteNonQuery to a string. I need to query the table and if the file name Does Not exist, then continue.

string[] files = Directory.GetFiles(@"C:\Documents and Settings\js91162\Desktop ",
        "R303717*.txt*", SearchOption.AllDirectories);
foreach (string file in files)
{
    string FileNameExt1 = Path.GetFileName(file);

    insertCommand.CommandText = @" 
            SELECT * FROM Import WHERE FileName == FileNameExt1;";
}
string contYes = insertCommand.ExecuteNonQuery();

if (string.IsNullOrEmpty(contYes))
{
    //more code
}

EDIT: added space in path so that slash doesn't eat quotation mark

Answer 1

ExecuteNonQuery is for non-queries. If you want to query data, use ExecuteReader

SqlDataReader myReader = insertCommand.ExecuteReader();
while(myReader.Read()) 
{
    Console.WriteLine(myReader.GetString(0)); //0 is the column-number
}

Answer 2

If you want to check if there is a row with some file name then you could also use ExecuteScalar with

SELECT COUNT(*) FROM Import WHERE FileName = @FileName

Of course you must also set parameter for the command. Then you can do

int count = Convert.ToInt32(insertCommand.ExecuteScalar());
if (count == 0)
{
  // code...
}

EDIT: The whole thing with parameters would look something like this:

selectCommand.CommandText = "SELECT COUNT(*) FROM Import Where FileName = @FileName";
selectCommand.Parameters.Add("@FileName", SqlDbType.NVarChar); // Use appropriate db type here
insertCommand.CommandText = "INSERT INTO Import (FileName, ...) VALUES (@FileName, ...");
insertCommand.Parameters.Add("@FileName", SqlDbType.NVarChar);
// Add your other parameters here.
// ...
foreach (string file in files) 
{ 
  var fileName = Path.GetFileName(file);
  selectCommand.Parameters[0].Value = Path.GetFileName(fileName);
  int count = Convert.ToInt32(selectCommand.ExecuteScalar());
  if (count == 0)
  {
    // File does not exist in db, add it.
    insertCommand.Parameters[0].Value = fileName;
    // Init your other parameters here.
    // ...

    insertCommand.ExecuteNonQuery(); // This executes the insert statement.
  }
}