public void Button1_OnClick(object sender, EventArgs e)
    { 

        string path = TextBox1.Text.ToString();
        string file = TextBox2.Text.ToString();
        DirectoryInfo dir = new DirectoryInfo(path);
        FileInfo[] bmpfiles = dir.GetFiles(file);
        foreach( FileInfo f in bmpfiles)
        {
            //add what you need to do with the file when found
            Label1.Text = "File Found";
        }
    }