SharePoint Workflow Association : Associate workflow to list or web programmatically

Hi,
It's very frequently required to attach/associate workflow to list or web programmatically. For a workflow a history list and task list is required.
History list is use to log activity/error occurred during workflow running span.
Task list is use to create and assign task for some approval etc. to user.
Workflow Association:- The binding of any workflow template to list or web is called workflow association.

Step. 1 Create a workflow history list.

public void CreateHistoryList(){
     using(SPSite site = new SPSite("Your web url")){
        using(SPWeb web = site.OpenWeb()){
           web.Lists.Add("YourHistoryListTitle","ListDescription",SPListTemplateType.WorkflowHistory);
        }
     }
}

Step. 2 Create a Workflow Task list.

public void CreateTaskList(){
using(SPSite site = new SPSite("Your web url")){
        using(SPWeb web = site.OpenWeb()){
           web.Lists.Add("YourTaskListTitle","ListDescription",SPListTemplateType.Tasks);
        }
     }
}

Step. 3 Associate workflow with web ( In case of Site Workflow)


 public void AddWorkflowAssociation(){childWeb.AllowUnsafeUpdates = true;

using(SPSite site = new SPSite("Your web url")){
using(SPWeb web = site.OpenWeb()){

//Add workflow association
SPWorkflowTemplate workflowTemplate = web.WorkflowTemplates.GetTemplateByName("YourWorkflowTemplateName", new CultureInfo(1033));
SPWorkflowAssociation association = SPWorkflowAssociation.CreateListAssociation(workflowTemplate, "Workflow Association Name",
web.Lists["TaskListTitle"], web.Lists["HistoryList"]);
//configures workflow assocition options
association.AllowManual = true;
association.AutoStartCreate = false;
association.AutoStartChange = false;
association.AllowAsyncManualStart = false;
web.WorkflowAssociations.Add(association);
web.Update();
}
     }
}

Step. 4 Associate workflow with web ( In case of List Workflow)


public void AddWorkflowAssociation(){childWeb.AllowUnsafeUpdates = true;
using(SPSite site = new SPSite("Your web url")){
        using(SPWeb web = site.OpenWeb()){
        //Add workflow association
        SPWorkflowTemplate workflowTemplate = web.WorkflowTemplates.GetTemplateByName("YourWorkflowTemplateName", new CultureInfo(1033));
        SPWorkflowAssociation association = SPWorkflowAssociation.CreateListAssociation(workflowTemplate, "Workflow Association Name",
                                web.Lists["TaskListTitle"], web.Lists["HistoryList"]);
        //configures workflow assocition options
        association.AllowManual = true;
        association.AutoStartCreate = false;
        association.AutoStartChange = false;
        association.AllowAsyncManualStart = false;
        SPList list = web.Lists.TryGetList("YourListTitle");
        list.WorkflowAssociations.Add(association);
        web.Update();
         }
     }
}

Now your workflow is associated with either list or web.