put your code in a try catch, and explicitly bubble up any errors that might occur;

you'll get a better error description than you are currently receiving:

public void Main()

{

[highlight="#ffff11"]try

{[/highlight]

// TODO: Add your code here

--System.IO.Path.Combine

String Filepath = System.IO.Path.Combine(Dts.Variables["User::FileLocation"].Value.ToString() , Dts.Variables["User::FileName"].Value.ToString());

if (

File.Exists(Filepath))

{

Dts.Variables["User::FileExistFlg"].Value = 1;

}

MessageBox.Show(Filepath);

MessageBox.Show(Dts.Variables["User::FileExistFlg"].Value.ToString());

Dts.TaskResult = (int)ScriptResults.Success;

[highlight="#ffff11"]}

catch (Exception ex)

{

Dts.Events.FireError(-1, "Main", ex.Message, "", 0);

Dts.TaskResult = (int)ScriptResults.Failure;

}[/highlight]

}