Gets or sets columns to map with the direction InputOutput.

The key is required for operation such as BulkUpdate and BulkMerge.


context.BulkMerge(list, options => 
        options.ColumnInputOutputExpression = entity => new {entity.ID, entity.Code}


The ColumnInputOutputExpression option let you choose specific properties in which you want to perform the bulk operations.

By example, when importing a file, you may have not data on all properties.