In order to use C# with the ArcGIS Platform I recommend that you review the ArcObjects API Reference for .NET, and in particular this ArcMap Overview.

Something to be aware of at the outset is that little (some annotation is one exception) or no spatial data is stored in *.mxd files. Consequently, I suspect that what you are looking to do is to access spatial data via layers in *.mxd files in order to locate their external sources and any applicable filters and use them to copy the data from its sources to an SQL Server repository.

In order to use C# with the ArcGIS Platform I recommend that you review the ArcObjects API Reference for .NET, and in particular this ArcMap Overview.

Something to be aware of at the outset is that little (some annotation is one exception) or no spatial data is stored in *.mxd files. Consequently, I suspect that what you are looking to do is to access spatial data via layers in *.mxd files in order to locate their external sources and any applicable filters and use them to copy the data from its sources to an SQL Server repository.