1.IIS->[网站]－>属性－》连接超时。默认为120秒
2.WEB.CONFIG 手工添加httpRuntime，如
<system.web>
<httpRuntime maxRequestLength="1000000" executionTimeout="2000" />
</system.web>
3.同步执行WEBSERVICE时，需要设置TIMEOUT属性，如
CompilerSvr.MyFavoritesService compiler=new FDN.DMS.Controls.CompilerSvr.MyFavoritesService();
compiler.Timeout =2000000; //毫秒

如果使用FILL一个很大的数据到table或dataset
DataTable retTable = new DataTable();
retTable.TableName = tablename;
SqlConnection con = new SqlConnection( m_SqlConnectionString );
con.Open ();
SqlDataAdapter sda = new SqlDataAdapter( sql, con );
sda.Fill ( retTable );
con.Close ();
return retTable;

即使你设置了connectstring <add key="connectionString" value="data source=(local);initial  id=sa;password=;packet size=8192;Connection Timeout=600" />仍然会超时，这时只有使用CommandTimeout：
SqlDataAdapter sda = new SqlDataAdapter();
SqlCommand sqlcmd = new SqlCommand();
DataSet dt = new DataSet();
SqlConnection con = new SqlConnection( m_SqlConnectionString );
con.Open ();
sqlcmd.Connection = con;
sqlcmd.CommandText = sql;
sqlcmd.CommandTimeout = 600;
//SqlDataAdapter sda = new SqlDataAdapter( sql, con );
sda.SelectCommand = sqlcmd;
sda.Fill(dt) ;
con.Close ();
return dt.Tables[0];