Yet Another Code Generator Templates

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Introduction

This is the second Yet Another Code Generator (YACGen) article. The first article gave a basic introduction of what YACGen does, an overview of schema creation and generating output. This article will cover basic template generation. The download includes the following sample templates used throughout the article.

Template	Description
BasicObjectsCS.tld	Basic C# representing a table object with properties
BuildHTMLTable.tld	Output table structure into HTML table
BuildHTMLTableB.tld	Output table structure into HTML table
BuildBasicGridView.tld	Build a ASP.Net gridview with only fields flagged in YACGen schema
BuildBasicGridViewCS.tld	Build gridview page C# code-behind file

There are corresponding .grp generation files for each template. These files assume the templates are located in C:\Program Files\YACGEN\Templates. You should be running YACGen release 2008.7.17 Beta 1.

Template Design

YACGen is a database schema driven code generator. It builds output based on codeless templates. The templates are similar to a report generator layout, with bands of logic and headers and footer. The difference being YACGen generates output based on a database layout.

The first example creates a template to output table properties to a HTML document similar to the following layout:

To create the template:

1. Move to the Template Layout tab
2. Select New Template File from the toolbar .

You are now ready to create your template. The highest level (root) gives you the option of post and pre template boxes. The contents of these two text boxes will appear at the beginning and end of the output document.

To save typing the appropriate sections are copied and pasted from the HTML file mocked up in an editor. Using this approach the bulk of the page can be copied and pasted and the appropriate schema properties inserted where required. The header section is pasted in the pre template text box and the closing HTML tags are placed in the post template text box.

There are a few properties that need replacing. The table name will appear as the document title as well as a header line. To insert a property, either type it or double click on the appropriate property from the properties list that appears when you enter a text box. Properties as surrounded by a <# and #> sequence. When you enter a template box a floating property list will appear:

Double click on any property in the list to insert the property. (Note: this is not a complete list.) The result will look something like this:

You can now add one or more sections. A section is a grouping of fields. The output fields are determined by the logic in the section. If no detail logic is supplied (see further in article on how to create conditional logic) output is generated for all fields for that section. You may have as many sections as you want.

The following image shows section row generation logic:

You can also drag sections to reorder or move them.

This next sample template is called BuildHTMLTable.tld in the included file. The file BuildHTMLTable.gpr will build output for all tables for the Northwind database.

In the first example all fields were output. Depending on what you are generating, you may only want to output a selection of fields. For example, for one section you may only want primary key fields, while in another section you may have different output depending on a field's data type.

To control the output, you may add conditional detail. Select the section to add the detail to and select the Add Detail toolbar button.

You can add as many conditional sections you want. The controls are described as follows:

Level	Process level. If you require multiple steps then create additional levels.
Description	Condition description
Data Type	Any Data Type, specific data groupings such as String, Decimal, Integer, Date or specific database data types
Field Type	All fields, all fields except primary keys, primary keys only and foreign keys only

The Conditions list provides an additional level of control. You can add as many conditional expressions as you wish within this box. Conditions are split into 3 columns: Property, Operator and Value.

Property represents a YACGen schema value. Operator represents a comparison operator, such as equal, great than or less than. Value is the value you are comparing against.

Below the list of conditions is the actual template. The template contents will be processed and output if all the conditions are met. If you are using conditions the section detail template is ignored.

By default all conditions in the condition list have to be met (and operation) to process the template. If you wish to perform an or operation, where the output is generated if only one or more of the conditions are met, click the Or checkbox. There is also an Empty Output checkbox. If you select this no output will be generated if all conditions are met. This is useful for conditions you wish to ignore.

The sections are evaluated in the order they are added. To minimize logic it is usually best to start with conditions that generate no output, then general logic and finish off with logic with no conditions (i.e. process everything) to catch anything the preceding levels missed. You can drag conditions to reorder as needed and use Ctrl+drag to make a copy of a condition.

In the first example, all fields were output into a formatted table. The length is output, even for image, currency and integer values where it isn't that useful. So the first condition would output all columns except width for currency, date, image and large text objects:

The second condition would output all columns for any remaining fields that didn't get processed in the first condition:

There is also a condition grid on the sections level. These conditions can be used to control if certain sections are processed.

Expressions

As we have seen, anything within the <# and #> sequence are evaluated by the template engine. YACGen can also return content based on conditions within the template layout itself. The expression syntax is <#Expresion\|\true value\|\false#>

The expression can be any Boolean YACGen property or a Python expression of the form <#Flag1 == "True"\|\Flag1 is set \|\Flag1 is set#>. (Note that Python expressions are case sensitive.) YACGen Boolean properties include IsPrimaryKey, IsForeignKey, IsVirtualField, IS_NULLABLE and ISIDENTITY. Other YACGen properties are stored as strings. For example: <#IS_NULLABLE\|\this field can store null values\|\this field doesn't store null values#>

The expression can span multiple lines in the template. If the second (false) evaluation string isn't specified, a blank string is returned if the expression evaluates to false. The following example demonstrates code generating a C# Integer variable declaration, with a question mark returned if the field is nullable.

YACGen includes the generic repetition operator REP. The REP operator simply repeats the sequence following REP while there are still fields to be processed for the current condition. For example, the following condition would return all primary key fields separated by a comma:

In addition, YACGen has a special property OrdinalMatched which is a counter that increases for every condition matched. as well as a number of flags that can be used to control template output. For example, you may wish to control what fields appear in a grid. In the field property page you can set up to 15 flags for each field as follows:

The pages generated require a data source to be defined in the Web.Config file. The data source name is populated using the database schema's Data Source Name property. To create a valid C# ASP.NET page you need the aspx and corresponding aspx.cs file. The included BuildBasicGridView.tld and BuildBasicGridViewCS.tld files builds the aspx file with a data source, select statement and gridview only with the columns specified by the Flag1 as well as the page code behind file.

YACGen Properties

One way of determining a property name is hovering over a value on the appropriate field and the control's tool tip showing the property name will appear. The majority of properties have suggested names, but you don't have to store formatting information in the Format property.

The following tables list available YACGen properties. They are grouped according to the object they apply to.

Field Properties

Property Name	Description	Example
NETDataType		Int32
FixedName
FKTFieldName
FKTNetDataType
FTKEY
KeyType
FKTABLE_NAME
AssociationType
IsAssociation
FKTABLE_ALIAS
FKPopulateLocal
FKPopulateLocalField
FKTFieldNameAlias
FKDirectStatement
FKSelectMethod
Width		10
AltFieldName		Category ID
Description
Format, Format2, Format3
Index		True, False
Validation1,Validation2
Validation2
ValidationMessage
Message
FKDataSource
MultiLine,MultiLine2,MultiLine3		True, False
CharWidth, CharWidth2,CharWidth3
CharRows, CharRows2,CharRows3
PixelWidth,PixelWidth2 PixelWidth3
PixelHeight,PixelHeight2 PixelHeight3
Custom1-4
Snippet1-2
DefaultValue
DefaultEmptyString		False
XCoord-3		0
YCoord-3		0
Flag1-15		True, False
FKDropDownEmptyMessage
TabStop
ControlType
COLUMN_NAME	Database field name	CategoryID
ORDINAL_POSITION	Datbase position	1
DATA_TYPE	Database data type	int
CHARACTER_MAXIMUM_LENGTH	Database field length
NUMERIC_PRECISION		10
NUMERIC_SCALE		0
COLLATION_NAME
COLUMN_DEFAULT
IS_NULLABLE		Boolean value. True, False
ISIDENTITY		Boolean value. True, False
ProperNETDataType		Int32
BaseDataType		Integer, Double, DateTime
GenericType		int
Ordinal		0
lastField	Last field in current condition?	True, False
IsPrimaryKey		Boolean value. True, False
IsForeignKey		Boolean value. True, False
IsVirtualField		Boolean value. True, False
Ignore		Boolean value. True, False

Database Properties

Property Name	Description	Example
DataSourceName
DBConnectionString
ServerName

Output Generation Properties

A first chance exception of type System.NullReferenceException occurred in C3I.CodegenTools.dll

Property Name	Description	Example
TemplateFile		C:\Program Files\YACGEN\Templates\TableSPs.tld
OutputDirectory		C:\Program Files\YACGEN\Output\
OutputLanguage		C#
DatabaseFile		C:\Program Files\YACGEN\Templates\northwind.dbd
DatabaseName		Northwind
TableName		Categories
Namespace
OutputFile		Category.txt
AuthorName		Stein Borge
Modified
NameSpace
Assembly
ShortDateTime
LongDateTime
ClassName
ConnectionString
Trademark
Company
FileVersion
Version
ShortTime		11:23 AM
Process	Determines what to process	All Tables, All Views, Single Table or View, All Tables and Views

Table Properties

Property Name	Description	Example
TableAltName
TableAltNameB		Categories
SelectSQL
TableFlag1-10		String value. True or False
TableMessage1-4
TableComment1
SQLSelectFields
SQLFromStatement
AllFieldsNoKeys	Current fields without key field separated by comma	string CategoryName,string Description,Byte[] Picture
AllFields	All fields separated by commas	Int32 CategoryID,string CategoryName,string Description,Byte[] Picture
AllKeys	All key fields separated by commas	Int32 CategoryID
LongDate		Tuesday, July 15, 2008
ShortDate		7/15/2008
LongTime		11:23:02 AM
ShortTime		4:39 PM
FieldCount		4
FieldWidth		8

History

July 17th 2008. First release