[WebMethod]
public DataSet GetDataSetForum2()
{
DataSet datasource = new DataSet();
string database = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|/topic.mdb;Persist Security Info=True";
string queryStr = "Select * from Comment";
OleDbConnection myConn = new OleDbConnection(database);
OleDbDataAdapter myDataAdapter = new OleDbDataAdapter(queryStr, myConn);
myConn.Open();
myDataAdapter.Fill(datasource, "Comment");
myConn.Close();
return datasource;
}

localhost.Topic topic = new localhost.Topic();

string topicId = Request.QueryString["TopicID"].ToString();

string id = "SELECT * FROM Post WHERE ForumID='" + topicId + "'";

datasource = topic.GetDataSetForum2(id);

GridView1.DataSource = datasource;

GridView1.DataBind();

topicid is a int not a string if that makes any difference.

So does a query string need to be within the webservice? I have noticed that there are two querystrings,however if I remove the querystring from the web service it doesnt display anything, as its not querying the table I think? I added the querystring which is located within the website however it stated that the topicid could not be found, so I added that but then it didnt like the response statement.

Thank you for your help

You are calling yout web method passing the id, but in your web method does not takes in any parameters. Check your web method GetDataSetForum2 definition.

datasource = topic.GetDataSetForum2(id);

I noticed that you method GetDataSetForum2() doesn't have any paramters set to it but you are assigning a parameter in your codes which is the id... so remove the id your code like

datasource = topic.GetDataSetForum2(id);

and replace with

datasource = topic.GetDataSetForum2();

But if you need to pass the id in the method then change you method to this

public DataSet GetDataSetForum2(string id)
{

//Your Logic goes here 

}