ADO.NET :: Field Method Missing With LINQ Query?

I want to access the data from datatable object. When i trying to get the fieldslist usng "Field" method. But I could not find the method with my table object. Eventhoguh i forcibly write a method and trying to access the fields, It is giving the below error for the first join in query. Rest of the lines are fine.

What is the reason behind it.

The errro: "Error 2 'LINQ2DB.SP_VS_OP' does not contain a definition for 'Field' and the best extension method overload 'System.Data.DataRowExtensions.Field<T>(System.Data.DataRow, string)' has some invalid arguments"

What is the meaningof the error. Shall i do any other changes in the query line?

var QueryChnl = from oSPOP in SPOP.AsEnumerable()
join oDiscChannel in DiscChannel.AsEnumerable() on oSPOP.Field<int>("spid") equals oDiscChannel.Field<int>("SPID")
join oChannel in Channel.AsEnumerable() on oDiscChannel.Field<int>("channel") equals oChannel.Field<int>("channelID")
where oSPOP.Mappingkey == 3200004
select new { oSPOP.Mappingkey, oChannel.channel, oDiscChannel.STATUS };