Can someone share part of code that create object data table and assign values to object?
You will use AutoCAD Map .NET API to do it.
You can download AutoCAD Map ObjectARX SDK (not AutoCAD ObjectARX SDK, which you probably already downloaded, if you have already been doing AutoCAD .NET API, which is necessary base knowledge/kill before you can go on with Map .NET API). As AutoCAD ObjectARX SDK, Map ObjectARX SDK comes with Map .NET API sample code. Included are sample code dealing with ObjectData.
You can also directly find sample code online from AutoCAD Map Development document (saving you from downloading Map ObjectARX SDK), such as here (for AutoCAD Map 2014, but since Map .NET API remains unchanged for many years, it applies to latest Map 2020):
HTH