C＃中的XML - 将命名空间添加到新的XML元素

The XML I post may be big, but my problem is rather simple. Please take a look at the second Dimensions tag. The first Dimension is automatically generated. The second one is created by me in C# script. The question is: how do I make my Dimension tag have the exact same namespaces ("xsi:type="RegularMeasureGroupDimension") as the generated one? Thanks for any help! The XML I post may be big, but my problem is ra