Developer Tips - Using the Field Checker

This post was written by geodatabase Product Engineer James MacKay. James works on the geodatabase development team and is responsible for a lot of the geodatabase SDK that is generated.

The IFieldChecker interface provides a way to validate fields for a specific workspace before they’re created. Reserved keywords, special characters and maximum field name lengths are properties that vary between different types of workspaces and DBMSs; the field checker will not only detect fields that violate these rules, but it will generate a “fixed” fields collection with a similar (but valid) name. There are three common cases where field checkers are useful:

• Creating new feature classes or tables
• Adding fields to existing datasets
• Generate target dataset fields for use in the feature data converter

A field checker should always be used whenever an application allows users to manually enter field names, but it’s a good defensive programming pattern to use them all of the time. The following code shows how to validate fields prior to a CreateTable or CreateFeatureClass call.

Geoprocessing users: The geoprocessor also exposes field checking capability. See this article for more information.

public IFields ValidateFields(IWorkspace workspace, IFields fields)

{

      // Create and initialize a field checker.

      IFieldChecker fieldChecker = new FieldCheckerClass();

      fieldChecker.ValidateWorkspace = workspace;

                 

      // Generate a validated fields collection.

      IFields validatedFields = null;

      IEnumFieldError enumFieldError = null;

      fieldChecker.Validate(fields, out enumFieldError, out validatedFields);

 

      // You can either notify the user of any errors or just skip this step.

      IFieldError fieldError = null;

      while ((fieldError = enumFieldError.Next()) != null)

      {

            Console.WriteLine("Error in field {0}: {1}", fieldError.FieldIndex, fieldError.FieldError);

      }

 

      // Return the validated fields.

      return validatedFields;

}