Take all text files in a folder and combine then into 1 - merge

Question

I'm trying to merge all my text files into one file.
The problem I am having is that the file names are based on data previously captured in my app. I don't know how to define my path to where the text files are, maybe. I keep getting a error, but the path to the files are correct.
What am I missing?
string filesread = System.AppDomain.CurrentDomain.BaseDirectory + #"\data\Customers\" + CustComboB.SelectedItem + #"\";
Directory.GetFiles(filesread);
using (var output = File.Create("allfiles.txt"))
{
foreach (var file in new[] { filesread })
{
using (var input = File.OpenRead(file))
{
input.CopyTo(output);
}
}
}
System.Diagnostics.Process.Start("allfiles.txt");
my error:
System.IO.DirectoryNotFoundException
HResult=0x80070003
Message=Could not find a part of the path 'C:\Users\simeo\source\repos\UpMarker\UpMarker\bin\Debug\data\Customers\13Dec2018\'.
I cant post a pic, but let me try and give some more details on my form.
I select a combobox item, this item is a directory. then I have a listbox that displays the files in my directory. I then have a button that executes my desires of combining the files. thanks

Answer 1

I finally got it working.
string path = #"data\Customers\" + CustComboB.SelectedItem;
string topath = #"data\Customers\";
string files = "*.txt";
string[] txtFiles;
txtFiles = Directory.GetFiles(path, files);
using (StreamWriter writer = new StreamWriter(topath + #"\allfiles.txt"))
{
for (int i = 0; i < txtFiles.Length; i++)
{
using (StreamReader reader = File.OpenText(txtFiles[i]))
{
writer.Write(reader.ReadToEnd());
}
}
System.Diagnostics.Process.Start(topath + #"\allfiles.txt");
}