数据库可以定义表不同列之间的计算公式，进行自动公式计算，但如何实现行上的动态公式计算呢？行由于可以动态扩展，在某些应用场景下将能很好的解决实际问题。这也是Excel为什么如何好用的一个重要原因，它可以建立单元格之间的勾稽关系，通过函数的方式实现强大的计算能力。
下面我们就探讨一下如何在WPF中实现一种基于行字段的动态公式计算，具体的示例如下所示。
1 项目结构
首先，在Visual Studio IDE中新建一个WPF应用程序WpfApp_DynCalc，并添加一个类DynCalc.cs，项目具体的结构如下图所示：
2 代码实现
在WPF中，UI界面是通过XAML语言实现的，主界面对应的文件为MainWindow.xaml，因此在Visual Studio中对文件MainWindow.xaml进行编辑，核心代码如下：
<Window x:Class="WpfApp_DynCalc.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="WPF动态计算示例" Height="350" Width="525">
<Grid>
<Grid.Resources>
<Style TargetType="DataGrid">
<!--网格线颜色-->
<Setter Property="CanUserResizeColumns" Value="false"/>
<Setter Property="Background" Value="#E6DBBB" />
<Setter Property="BorderBrush" Value="#d6c79b" />
<Setter Property="HorizontalGridLinesBrush">
<Setter.Value>
<SolidColorBrush Color="#d6c79b"/>
</Setter.Value>
</Setter>
<Setter Property="VerticalGridLinesBrush">
<Setter.Value>
<SolidColorBrush Color="#d6c79b"/>
</Setter.Value>
</Setter>
</Style>
<!--标题栏样式-->
<!--<Style TargetType="DataGridColumnHeader" >
<Setter Property="Width" Value="50"/>
<Setter Property="Height" Value="30"/>
<Setter Property="FontSize" Value="14" />
<Setter Property="Background" Value="White" />
<Setter Property="FontWeight" Value="Bold"/>
</Style>-->
<Style TargetType="DataGridColumnHeader">
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="MinWidth" Value="0" />
<Setter Property="MinHeight" Value="28" />
<Setter Property="Foreground" Value="#323433" />
<Setter Property="FontSize" Value="14" />
<Setter Property="Cursor" Value="Hand" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="DataGridColumnHeader">
<Border x:Name="BackgroundBorder" BorderThickness="0,1,0,1"
BorderBrush="#e6dbba"
Width="Auto">
<Grid >
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<ContentPresenter Margin="0,0,0,0" VerticalAlignment="Center" HorizontalAlignment="Center"/>
<Path x:Name="SortArrow" Visibility="Collapsed" Data="M0,0 L1,0 0.5,1 z" Stretch="Fill" Grid.Column="2" Width="8" Height="6" Fill="White" Margin="0,0,50,0"
VerticalAlignment="Center" RenderTransformOrigin="1,1" />
<Rectangle Width="1" Fill="#d6c79b" HorizontalAlignment="Right" Grid.ColumnSpan="1" />
<!--<TextBlock Background="Red">
<ContentPresenter></ContentPresenter></TextBlock>-->
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Setter Property="Height" Value="25"/>
</Style>
<!--行样式触发-->
<!--背景色改变必须先设置cellStyle 因为cellStyle会覆盖rowStyle样式-->
<Style TargetType="DataGridRow">
<Setter Property="Background" Value="#F2F2F2" />
<Setter Property="Height" Value="25"/>
<Setter Property="Foreground" Value="Black" />
<Style.Triggers>
<!--隔行换色-->
<Trigger Property="AlternationIndex" Value="0" >
<Setter Property="Background" Value="#e7e7e7" />
</Trigger>
<Trigger Property="AlternationIndex" Value="1" >
<Setter Property="Background" Value="#f2f2f2" />
</Trigger>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="LightGray"/>
<!--<Setter Property="Foreground" Value="White"/>-->
</Trigger>
<Trigger Property="IsSelected" Value="True">
<Setter Property="Foreground" Value="Black"/>
</Trigger>
</Style.Triggers>
</Style>
<!--单元格样式触发-->
<Style TargetType="DataGridCell">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="DataGridCell">
<TextBlock TextAlignment="Center" VerticalAlignment="Center" >
<ContentPresenter />
</TextBlock>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<!--<Setter Property="Background" Value="White"/>
<Setter Property="BorderThickness" Value="0"/>-->
<Setter Property="Foreground" Value="Black"/>
</Trigger>
</Style.Triggers>
</Style>
</Grid.Resources>
<DataGrid Name="dgrid" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top" Height="256" Width="498" AutoGenerateColumns="False" >
<DataGrid.Columns>
<DataGridTextColumn Header="指标" Binding="{Binding Zb}" Width="118"/>
<DataGridTextColumn Header="值" Binding="{Binding Value}" Width="100"/>
<DataGridTextColumn Header="公式" Binding="{Binding Formula}" Width="188"/>
</DataGrid.Columns>
</DataGrid>
<Button Content="计 算" HorizontalAlignment="Left" Margin="419,281,0,0" VerticalAlignment="Top" Width="85" Click="Button_Click_1" Height="28" />
<TextBlock Name="lblResult" HorizontalAlignment="Left" Margin="28,281,0,0" TextWrapping="Wrap" Text="" VerticalAlignment="Top"/>
</Grid>
</Window> 从代码中可知，界面中通过DataGrid控件生成一个表格，其中绑定了相关的变量，进行动态的数据展现。而计算但你的后台逻辑是通过Button_Click_1事件实现的，后台代码文件为MainWindow.xaml.cs，编辑后台文件MainWindow.xaml.cs，核心代码如下:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Collections.ObjectModel;
namespace WpfApp_DynCalc
{
/// <summary>
/// MainWindow.xaml 的交互逻辑
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
ObservableCollection<Dynformula> ofs = new ObservableCollection<Dynformula>();
ofs.Add(new Dynformula { Zb = "A", Value = "1", Formula = "" });
ofs.Add(new Dynformula { Zb = "B", Value = "2", Formula = "2*A+1" });
ofs.Add(new Dynformula { Zb = "C", Value = "3", Formula = "B*B" });
ofs.Add(new Dynformula { Zb = "D", Value = "4", Formula = "C-2" });
ofs.Add(new Dynformula { Zb = "Z", Value = "5", Formula = "D+C" });
this.dgrid.ItemsSource = ofs;
}
private void Button_Click_1(object sender, RoutedEventArgs e)
{
this.lblResult.Text = "计算...";
this.dgrid.ItemsSource= DynCalc.CalcScript(ref this.dgrid);
this.lblResult.Text = "计算完成!";
}
}
public class Dynformula
{
private string zb;
public string Zb
{
get { return zb; }
set { zb = value; }
}
private string value;
public string Value
{
get { return this.value; }
set { this.value = value; }
}
private string formula;
public string Formula
{
get { return formula; }
set { formula = value; }
}
}
} 其中计算按钮的逻辑中，调用了一个核心方法DynCalc.CalcScript(ref this.dgrid)，它在类文件DynCalc.cs中定义，其核心带代码如下所示：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace WpfApp_DynCalc
{
using System.Collections.ObjectModel;
using System.Windows;
using System.Windows.Controls;
using System.Reflection;
using System.Globalization;
using Microsoft.CSharp;
using System.CodeDom;
using System.CodeDom.Compiler;
public static class DynCalc
{
public static ObservableCollection<Dynformula> CalcScript(ref DataGrid dgrid)
{
CSharpCodeProvider objCSharpCodePrivoder = new CSharpCodeProvider();
ICodeCompiler objICodeCompiler = objCSharpCodePrivoder.CreateCompiler();
CompilerParameters objCompilerParameters = new CompilerParameters();
objCompilerParameters.ReferencedAssemblies.Add("System.dll");
objCompilerParameters.GenerateExecutable = false;
objCompilerParameters.GenerateInMemory = true;
CompilerResults cr = objICodeCompiler.CompileAssemblyFromSource(objCompilerParameters, GenerateCode(ref dgrid));
if (cr.Errors.HasErrors)
{
Console.WriteLine("编译错误：");
foreach (CompilerError err in cr.Errors)
{
Console.WriteLine(err.ErrorText);
}
return null;
}
else
{
// 通过反射，调用实例
Assembly objAssembly = cr.CompiledAssembly;
object objDynCalc = objAssembly.CreateInstance("DynamicCodeGenerate.RunScript");
//MethodInfo objMI = objHelloWorld.GetType().GetMethod("OutPut");
//Console.WriteLine(objMI.Invoke(objHelloWorld, null));
ObservableCollection<Dynformula> ofsnew = new ObservableCollection<Dynformula>();
//循环datagrid进行公式计算并赋值
for (int i = 0; i < dgrid.Items.Count; i++)
{
Dynformula item = dgrid.Items[i] as Dynformula;
if (item == null)
{
break;
}
string zb = item.Zb;
PropertyInfo pinfo = objDynCalc.GetType().GetProperty(zb);
if (pinfo != null && pinfo.CanRead) {
//获取属性get值
object obj_Name = pinfo.GetValue(objDynCalc, null);
// item.Value = obj_Name.ToString();
ofsnew.Add(new Dynformula { Zb = item.Zb, Value = obj_Name.ToString(), Formula = item.Formula});
}
}
return ofsnew;
}
}
/// <summary>
/// 计算逻辑C#脚本动态构建
/// </summary>
/// <param name="dgrid">存有指标以及指标计算公式的datagrid</param>
/// <returns>C#脚本</returns>
static string GenerateCode(ref DataGrid dgrid)
{
StringBuilder sb = new StringBuilder();
StringBuilder sb构建函数内容 = new StringBuilder();
sb.Append("using System;");
sb.Append(Environment.NewLine);
sb.Append("namespace DynamicCodeGenerate");
sb.Append(Environment.NewLine);
sb.Append("{");
sb.Append(Environment.NewLine);
sb.Append(" public class RunScript");
sb.Append(Environment.NewLine);
sb.Append(" {");
//------------------------------------------------------------
for(int i=0;i<dgrid.Items.Count;i++)
{
Dynformula item = dgrid.Items[i] as Dynformula;
if (item == null)
{
break;
}
string zb = item.Zb;
sb.Append(Environment.NewLine);
sb.AppendFormat(" public double _{0};", item.Zb);
sb.Append(Environment.NewLine);
sb.AppendFormat(" public double {0}",item.Zb);
sb.Append(Environment.NewLine);
sb.Append(" {");
sb.Append(Environment.NewLine);
if (item.Formula.Trim() != "")
{
sb.Append(" set{ "+item.Zb+"=value;}" );
sb.Append(Environment.NewLine);
sb.Append(" get{return "+ item.Formula + ";}");
}
else
{
sb.Append(" set{ _" + item.Zb + "=value;}");
sb.Append(Environment.NewLine);
sb.Append(" get{return _"+item.Zb+";} ");
sb.Append(Environment.NewLine);
sb构建函数内容.Append(" _" + item.Zb + "=" + item.Value);
}
sb.Append(Environment.NewLine);
sb.Append(" }");
sb.Append(Environment.NewLine);
}
//--------------------------------------------
//构造函数进行赋值
sb.Append(Environment.NewLine);
sb.Append(" public RunScript()");
sb.Append(Environment.NewLine);
sb.Append(" {");
sb.Append(Environment.NewLine);
sb.AppendFormat(" {0};",sb构建函数内容.ToString());
sb.Append(Environment.NewLine);
sb.Append(" }");
sb.Append(Environment.NewLine);
//----------------------------------------------
sb.Append(Environment.NewLine);
sb.Append(" public string OutPut()");
sb.Append(Environment.NewLine);
sb.Append(" {");
sb.Append(Environment.NewLine);
sb.Append(" return \"Hello world!\";");
sb.Append(Environment.NewLine);
sb.Append(" }");
//-----------------------------------------
sb.Append(Environment.NewLine);
sb.Append(" }");
sb.Append(Environment.NewLine);
sb.Append("}");
string code = sb.ToString();
Console.WriteLine(code);
return code;
}
}
} 其中用到了C#内置的CSharpCodeProvider类，它内置了一个C#语言的编译器，可以用来动态的执行C#代码，因此，单击按钮后，就需要在表格中获取指标的值，并动态构建脚本来执行，这样就可以获取到对应的变量值，并显示到UI上。
3 效果
运行程序，其中值列的值为初始值，点击计算后会根据公式列配置进行动态计算，初始化界面如下:
可见现在的值是根据公式配置进行动态计算的。当然代码经过扩展还可以支持函数和简单的逻辑判断，如if ...else等。实现更强大的逻辑处理。