Repository.cs

protected virtual Type[] GetKeysTypes()
{
    var model = Context.Set<TEntity>().GetService<IDbContextServices>().Model;
    var entityType = model.FindEntityType(typeof(TEntity).ToString());
    return entityType.FindPrimaryKey()
                 .Properties
                 .Select(p => p.ClrType)
                 .ToArray();
}

public TEntity GetByEntityId(string entityId)
{
    var types = this.GetKeysTypes();
    var strKeys = entityId.Split('$');

    if(types.Length != strKeys.Length)
    {
        throw new Exception("Error on entityId");
    }

    var objKeys = new object[strKeys.Length];
    for(int i = 0; i < objKeys.Length; i++)
    {
        objKeys[i] = Convert.ChangeType(strKeys[i], types[i]);
    }

    return Context.Set<TEntity>().Find(objKeys);
}