Okay here is what I did.
MyEntities myE = new MyEntities();
var objCtx = ((System.Data.Entity.Infrastructure.IObjectContextAdapter)myE).ObjectContext;
objCtx.ExecuteStoreCommand("Truncate table SomeEntityTable");
SomeEntityTable table = new SomeEntityTable();
table.someFieldName1 = "Value1";
table.someFiledName2 = "Value2";
...
myE.Add(table);
myE.SaveChanges();