定义：根据提供的数据或参数返回几种可能类中的一种。
示例：实现计算器功能，要求输入两个数和运算符号，得到结果。
结构图：
HTML：
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Simple Factory Demo</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="txtNumA" runat="server" Width="50px"></asp:TextBox>
<asp:DropDownList ID="ddlOperateType" runat="server">
<asp:ListItem Selected="True">+</asp:ListItem>
<asp:ListItem>-</asp:ListItem>
<asp:ListItem>*</asp:ListItem>
<asp:ListItem>/</asp:ListItem>
</asp:DropDownList>
<asp:TextBox ID="txtNumB" runat="server" Width="50px"></asp:TextBox>
<asp:Button ID="btnGetResult" runat="server" Text="=" OnClick="btnGetResult_Click" />
<asp:TextBox ID="txtResult" runat="server" Width="50px"></asp:TextBox>
<asp:Label ID="lblMessage" runat="server" ForeColor="Red"></asp:Label>
</div>
</form>
</body>
</html>
运算类：
/// <summary>
/// Operation 运算类
/// </summary>
public class Operation
{
public double NumberA { get; set; } public double NumberB { get; set; } public virtual double GetResult()
{
return ;
}
减加乘除类：
/// <summary>
/// 加法类
/// </summary>
public class OperateAdd : Operation
{
public override double GetResult()
{
double result = ;
result = NumberA + NumberB; return result;
} } /// <summary>
/// 减法类
/// </summary>
public class OperateSub : Operation
{
public override double GetResult()
{
double result = ;
result = NumberA - NumberB; return result;
} } /// <summary>
/// 乘法类
/// </summary>
public class OperateMul : Operation
{
public override double GetResult()
{
double result = ;
result = NumberA * NumberB; return result;
}
} /// <summary>
/// 除法类
/// </summary>
public class OperateDiv : Operation
{
public override double GetResult()
{
double result = ;
if (NumberB == )
throw new Exception("被除数不能为0");
result = NumberA / NumberB; return result;
}
}
简单工厂类：
/// <summary>
/// 简单运算工厂类
/// </summary>
public class OperationFactory
{
public static Operation CreateOperate(string operate)
{
Operation oper = null; switch (operate)
{
case "+":
oper = new OperateAdd();
break;
case "-":
oper = new OperateSub();
break;
case "*":
oper = new OperateMul();
break;
default:
oper = new OperateDiv();
break;
} return oper;
}
}
客户端调用：
protected void btnGetResult_Click(object sender, EventArgs e)
{
lblMessage.Text = ""; try
{
Operation opeation;
opeation = OperationFactory.CreateOperate(ddlOperateType.SelectedValue);
opeation.NumberA = Convert.ToDouble(txtNumA.Text);
opeation.NumberB = Convert.ToDouble(txtNumB.Text); double result = opeation.GetResult(); txtResult.Text = result.ToString();
}
catch (Exception ex)
{
lblMessage.Text = ex.Message;
}
}