assign lookup of accountId contact value on case field (Compile Error: Invalid foreign key relationship: Contact.cases )

Question

i'm fetching data from soql need to insert account lookup value(accountId) and contact lookup value (ContactID) in case create from email services

here is my code:

String con_Email = envelope.fromAddress;

    //write soql and checking sender email & existing email of contact same
    List<Contact> conList = [SELECT Id, AccountID, Block_Email__c, Email, (SELECT AccountId, ContactId FROM cases) FROM contact WHERE email =: con_Email LIMIT 1];

    //Checking list size is greater then 0 and not eqaul to null
    if(conList.size()>0 && conList != null){

        //if Block Email checkbox true then email will not get into salesforce
        if(conList[0].Block_Email__c == true){

        }
        // if sender email & existing email of contact same create activity (task) 
        else if(conList[0].email == con_Email.trim()) {
            //Creating case
            Case cs = new Case();
            cs.Subject = email.subject;
            cs.Contact = conList[0].cases.ContactId;
            cs.Account = conList[0].AccountID;
            cs.Origin = 'E-Mail - FMB#1';
            cs.Description = email.plainTextBody;
            insert cs;

Answer 1

Change the following lines.

cs.Contact = conList[0].cases.ContactId;
cs.Account = conList[0].AccountID;

to

cs.ContactId = conList[0].Id;
cs.AccountId = conList[0].AccountID;

You will get contact id directly. You don't need to get it from cases list. Since you are using inner query all the cases will be having same contact id.