Programming Entity Framework - Cdn.oreilly.com

When T4 generates the new classes, if it determines that the MaxLength is needed, it
will write out a setter that includes the MaxLength validation; otherwise, the original
setter will be called. You’ll also need to make a small change a few lines lower, to ensure
that the field required by the validation is created—an if statement that already tests for
generateAutomaticProperty also must test hasMaxLengthAttrib.
Figure 13-5 shows the relevant section of the template after the changes from Example
13-14 have been made as well as the change to check the value of
hasMaxLengthAttrib.
Figure 13-5. Placement of template modifications for MaxLength
validation
Once you have the new code in place, the validation will automatically be part of your
generated class. Example 13-15 shows the addressed and Street1 properties of the
Address class using the modified template. The addressed property was not
impacted because it does not have a MaxLength attribute, but the Street1 property
now has validation code using the MaxLength value, 50, found in the metadata.
Example 13-15. The validation for Address.Street1 as generated from the modified
template
public int addressID
{