四、属性的生成
这些生成的属性是可读写的。这就需要将HasGet和HasSet两个属性设为true，然后分别将get和set方法中的语句分别加到GetStatements和SetStatements中。
下面是生成构造函数的源代码：
Add和Save方法生成
使用C# 2.0实现语言无关的代码生成器
在数据表类中每个属性代表数据表的一个字段，名子就是字段名。这些属性和保存字段的全局变量一一对应。下面是具体的实现代码：
private void GenerateProperties()
{
String fieldname = "", fieldtype = "";
foreach (XmlNode xn in m_Xml.DocumentElement.ChildNodes)
{
fieldname = xn.Name;
fieldtype = xn.Attributes["type"].Value;
CodeMemberProperty property = new CodeMemberProperty();
property.Attributes = MemberAttributes.Public | MemberAttributes.Final;
property.Name = fieldname;
property.Type = new CodeTypeReference(fieldtype);
property.HasGet = true;
property.HasSet = true;
CodeVariableReferenceExpression field = new CodeVariableReferenceExpression("m_" + fieldname);
// 产生 return m_property
CodeMethodReturnStatement propertyReturn = new CodeMethodReturnStatement(field);
property.GetStatements.Add(propertyReturn);
// 产生 m_property = value;
CodeAssignStatement propertyAssignment = new CodeAssignStatement(field, new CodePropertySetValueReferenceExpression());
property.SetStatements.Add(propertyAssignment);
m_Class.Members.Add(property);
}
}
构造函数的生成
构造函数的主要工作是打开数据表。如果数据表不存在，就创建这个数据表文件。在编写代码之前，需要先定义三个全局变量。因为这三个全局变量在程序中会多次用到。它们的类型都是CodeVariableReferenceExpression。这个类型变量其实在生成源码中的作用就是对某一个变量的引用。具体的实现代码如下：
private CodeVariableReferenceExpression m_XmlFileExpression;
private CodeVariableReferenceExpression m_XmlExpression;
private CodeVariableReferenceExpression m_AddFlagExpression;
private void InitVariants()
{
m_XmlFileExpression = new CodeVariableReferenceExpression("m_XmlFile");
m_XmlExpression = new CodeVariableReferenceExpression("m_xml");
m_AddFlagExpression = new CodeVariableReferenceExpression("m_AddFlag");
}
Add方法只有一条语句，功能是将m_AddFlag设为true，以使数据表类处于加入状态。Save方法比较复杂。它的功能是当m_AddFlag为true时在数据表文件的最后加入一条记录，并保存。具体实现代码如下：
private void GenerateMethods()
{
CodeTypeReference voidReference = new CodeTypeReference("System.void");
//产生Add方法
CodeMemberMethod add = new CodeMemberMethod();
add.ReturnType = voidReference;
add.Name = "add";
add.Attributes = MemberAttributes.Public | MemberAttributes.Final;
CodeAssignStatement assignAddTrue = new CodeAssignStatement(m_AddFlagExpression, new CodePrimitiveExpression(true));
add.Statements.Add(assignAddTrue);
m_Class.Members.Add(add);
//产生Save方法
CodeMemberMethod save = new CodeMemberMethod();
save.ReturnType = voidReference;
save.Name = "save";
save.Attributes = MemberAttributes.Public | MemberAttributes.Final;
System.Collections.Generic.List<CodeStatement> ifStatements = new System.Collections.Generic.List<CodeStatement>();
//产生 "XmlNode xn = m_xml.CreateNode(XmlNodeType.Element, "item", "");"
CodeVariableDeclarationStatement xmlNode = new CodeVariableDeclarationStatement("System.Xml.XmlNode", "xn");
CodeMethodInvokeExpression createNode = new CodeMethodInvokeExpression(m_XmlExpression, "CreateNode", new CodeExpression[] {new CodeVariableReferenceExpression("System.Xml.XmlNodeType.Element"), new CodePrimitiveExpression("item"), new CodePrimitiveExpression("") });
xmlNode.InitExpression = createNode;
ifStatements.Add(xmlNode);
//产生 "XmlAttribute xa = null; "
CodeVariableDeclarationStatement xmlAttr = new CodeVariableDeclarationStatement("System.Xml.XmlAttribute", "xa");
xmlAttr.InitExpression = new CodePrimitiveExpression(null);
ifStatements.Add(xmlAttr);
//产生字段属性
CodeStatementCollection statements = new CodeStatementCollection();
foreach (XmlNode xn in m_Xml.DocumentElement.ChildNodes)
{
CodeMethodInvokeExpression createAttribute = new CodeMethodInvokeExpression(m_XmlExpression,
"CreateAttribute", new CodePrimitiveExpression(xn.Name));
CodeAssignStatement assignxa = new CodeAssignStatement(new CodeVariableReferenceExpression("xa"), createAttribute);
CodeMethodInvokeExpression invokeToString = new CodeMethodInvokeExpression(new CodeVariableReferenceExpression("m_" + xn.Name), "ToString");
CodeAssignStatement assignValue = new CodeAssignStatement(new CodeVariableReferenceExpression("xa.Value"), invokeToString);
CodeMethodInvokeExpression invokeAppend = new CodeMethodInvokeExpression(new CodeVariableReferenceExpression("xn.Attributes"), "Append", new
CodeVariableReferenceExpression("xa"));
statements.Add(invokeAppend);
ifStatements.Add(assignxa);
ifStatements.Add(assignValue);
ifStatements.Add(statements[0]);
}
// 产生 "m_xml.DocumentElement.AppendChild(xn);"
CodeMethodInvokeExpression invokeAppendChild = new CodeMethodInvokeExpression(new CodeVariableReferenceExpression("m_xml.DocumentElement"), "AppendChild", new CodeVariableReferenceExpression("xn"));
statements.Clear();
statements.Add(invokeAppendChild);
ifStatements.Add(statements[0]);
// 产生 "m_xml.Save(m_XmlFile);"
CodeMethodInvokeExpression invokeSave = new CodeMethodInvokeExpression(m_XmlExpression, "Save", m_XmlFileExpression);
statements.Clear();
statements.Add(invokeSave);
ifStatements.Add(statements[0]);
// 产生 "m_AddFlag = false;"
CodeAssignStatement assignAddFalse = new CodeAssignStatement(m_AddFlagExpression, new CodePrimitiveExpression(false));
ifStatements.Add(assignAddFalse);
// 产生if语句: "if (m_AddFlag)"
CodeConditionStatement ifStatement = new CodeConditionStatement(m_AddFlagExpression, ifStatements.ToArray());
save.Statements.Add(ifStatement);
m_Class.Members.Add(save);
}
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