EF CodeFirst: Either the parameter @objname is ambiguous or the claimed @objtype (COLUMN) is wrong

If you're using Code First and have (an) existing Migration script(s) and are trying to overwrite a change (i.e. renaming a column) that has since been deleted, then you'll get that error output. Simplest way is to delete the migration script, Add-Migration via NuGet, and then update the database.

This is because of name Conflict of Class (Model) names with other reserved or generated ones, when auto creates the tables and ... .

Considering that EF Code First creates the intervene tables to relate 2 or more tables using name of tables for derived intervene table, so when you use a class name that employs a name like the intervene tables, we'll get such this ambiguous error.

For example if you have a Question class which has an Answer navigation property the internal model metadata will contain a reference called QUESTION_ANSWER

To solve this, try to change the class names (used for generating tables) and ensure their uniqueness.

I got this with Entity Framework 6 when trying to rename a foreign key in my migrations script using the Sql(" ... ") method. The workaround I had was to use square brackets around the name:

i.e. changing this:

sp_rename 'FK_dbo.tablename_dbo.othertablename_fieldname', 'FK_dbo.tablename_dbo.othertablenewname_fieldnewname', 'object'

...to this:

sp_rename '[FK_dbo.tablename_dbo.othertablename_fieldname]', 'FK_dbo.tablename_dbo.othertablenewname_fieldnewname', 'object'

SQL Server is then able to find the foreign key.