I tried like this,
threadvalues = new NameValueCollection();
threadvalues["Body"] = "My Test Body"
threadvalues["Subject"] = " My Test Title";
threadvalues["PostDate"] = testdate.ToString("dd/mm/yyyy");
It didn't created the thread. It thrown an error.
In the above code testdate is DateTime type.So I converted as String.
Please suggest how to update the PostDate field.