public void Modify( 
   TableDescription tableDescription
)

// Removing all fields from 'Parcels' table except following 
// Tax_Code
// Parcel_Address
      

// The table to remove fields
string tableName = "Parcels";

TableDefinition tableDefinition = geodatabase.GetDefinition<TableDefinition>(tableName);
IReadOnlyList<Field> fields = tableDefinition.GetFields();

// Existing fields from 'Parcels' table
Field taxCodeField = fields.First(f => f.Name.Equals("Tax_Code"));
Field parcelAddressField = fields.First(f => f.Name.Equals("Parcel_Address"));

FieldDescription taxFieldDescription = new FieldDescription(taxCodeField);
FieldDescription parcelAddressFieldDescription = new FieldDescription(parcelAddressField);
      
// Fields to retain in modified table
List<FieldDescription> fieldsToBeRetained =new List<FieldDescription>()
{
  taxFieldDescription, parcelAddressFieldDescription 
};

// New description of the 'Parcels' table with the 'Tax_Code' and 'Parcel_Address' fields
TableDescription modifiedTableDescription = new TableDescription(tableName, fieldsToBeRetained);

SchemaBuilder schemaBuilder = new SchemaBuilder(geodatabase);

// Remove all fields except the 'Tax_Code' and 'Parcel_Address' fields
schemaBuilder.Modify(modifiedTableDescription);
schemaBuilder.Build();