How to turn off cascade delete in Entity Framework Core 1.0 RTM

Hi I have MVC 6 application with Entity Framework Core 1.0 RTM and SQL server, when I try to generate database tables, I got "Introducing FOREIGN KEY constraint may cause cycles or multiple cascade paths" error.

My model classes are as below:

Category Model:

 public class Category
{
    public Category()
    {
        this.VariableSettings = new List<VariableSetting>();
    }
    public int CategoryId { get; set; }

    public string CategoryName { get; set; }

    public List<VariableSetting> VariableSettings { get; set; }

    public List<Station> Stations { get; set; }
}

Station Model:

 public class Station
{
    public int StationId { get; set; }
    public string StationName { get; set; }

    public double? Longitude { get; set; }
    public double? Latitude { get; set; }

    public List<VariableRecord> VariableRecords { get; set; }

    public int CategoryID { get; set; }
    public Category Category { get; set; }
}

VariableRecord Model:

 public class VariableRecord
{
    [Key]
    public int VariableRecordId { get; set; }
    public double Value { get; set; }
    public DateTime RecordDate { get; set; }

    public int StationId { get; set; }
    public Station Station { get; set; }

    public int VarSettingId{ get; set; }
    public virtual VariableSetting VariableSetting { get; set; }
}

VariableSetting Model:

public class VariableSetting
{
    [Key]
    public int VarSettingId { get; set; }
    public int Sequence { get; set; }
    public double? MinimumValue { get; set; }
    public double? MaximumValue { get; set; }

    public int CategoryId { get; set; }
    public virtual Category Category { get; set; }

    public int VariableId { get; set; }
    public Variable Variable { get; set; }

    public List<VariableRecord> VariableRecords { get; set; }
}

Variable Model:

 public class Variable
{
    public int VariableId { get; set; }

    public string VariableName { get; set; }

    public string Description { get; set; }

    public string Unit { get; set; }

    public List<VariableSetting> VariableSettings { get; set; }
}

So, there are too Cascade delete routes in my codes Category->Station->VariableRecord and Category->VariableSetting->VariableRecord, so I am trying to diable the route Category->VariableSetting->VariableRecord in the context class with Fluent API as below:

builder.Entity<VariableRecord>()
        .HasOne(pt => pt.VariableSetting)
        .WithMany(p => p.VariableRecords)
        .HasForeignKey(pt => pt.VarSettingId)
        .OnDelete(DeleteBehavior.Cascade);

However I still got same as below:

System.Data.SqlClient.SqlException (0x80131904): Introducing FOREIGN KEY constraint 'FK_VariableSetting_Category_CategoryId' on table 'VariableSetting' may cause cycles or multiple cascade paths.Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

I have been stuck on these codes for couple of days but still went nowhere, please help!