look man i solve it; i try it locally and i get the same error and the new modifications are below:
StringBuilder log = new StringBuilder();
string path = @"C:/Documents and Settings/aj99823/Desktop/project/" + DateTime.Now.ToString("yyyy-MM-dd");
if (!File.Exists(path))
{
log = new StringBuilder(path);
File.WriteAllText(path, "Hello World");
}
else
{
File.AppendAllText(path, "Hello World");
}
if this help you please rate
best regards