/// <summary>
/// Evaluates a simple expression, given via the parameter <paramref name="parameter"/>.
/// </summary>
/// <remarks>
/// This converter will often be used in XAML files. Note that in XAML, an attribute beginning with a <c>'{'</c> character
/// is interpreted as an invocation of a markup extension. So the expression "{0} + 5" must be escaped like this:
/// <c>"{}{0} + 5"</c>. Note also that the boolean AND operator (<c>"&&"</c>) must be escaped too like this: <c>"{}{0} && true"</c>.
/// </remarks>
/// <param name="values">The values used for the variables {0} .. {n}.</param>
/// <param name="targetType">Type to that the evaluated result should be converted.</param>
/// <param name="parameter">String containing the expression. Variables can be accessed via numbers in
/// curly braces, for example "!({0} || {2})". The variables are mapped to the values specified by
/// the <paramref name="values"/> array.</param>
/// <param name="result">Will return the evaluated result of the given <paramref name="targetType"/>.</param>
public bool Convert(IDataDescriptor[] values, Type targetType, object parameter, out object result)
{
result = null;
string expression = parameter as string;
if (string.IsNullOrEmpty(expression))
{
return(false);
}
try
{
// We're using an expression parser from "devilplusplus", "C# Eval function"
// See http://www.codeproject.com/KB/dotnet/Expr.aspx
// The parser was slightly adapted to our needs:
// - To access a variable, the variable identifier has to be written in curly braces, for example:
// {0} + {1}
Parser ep = new Parser();
Evaluator evaluator = new Evaluator();
ParameterVariableHolder pvh = new ParameterVariableHolder();
// The used expression parser supports access to static functions for those of the parameters whose type is a class.
// We could add classes here like the code commented out below. To access a static member on the string class,
// the expression could be for example: {string}.{Empty}
// For now, we don't need this functionality, so we don't add types (Albert, 2009-04-22).
//pvh.Parameters["char"] = new Parameter(typeof(char));
//pvh.Parameters["sbyte"] = new Parameter(typeof(sbyte));
//pvh.Parameters["byte"] = new Parameter(typeof(byte));
//pvh.Parameters["short"] = new Parameter(typeof(short));
//pvh.Parameters["ushort"] = new Parameter(typeof(ushort));
//pvh.Parameters["int"] = new Parameter(typeof(int));
//pvh.Parameters["uint"] = new Parameter(typeof(uint));
//pvh.Parameters["long"] = new Parameter(typeof(string));
//pvh.Parameters["ulong"] = new Parameter(typeof(ulong));
//pvh.Parameters["float"] = new Parameter(typeof(float));
//pvh.Parameters["double"] = new Parameter(typeof(double));
//pvh.Parameters["decimal"] = new Parameter(typeof(decimal));
//pvh.Parameters["DateTime"] = new Parameter(typeof(DateTime));
//pvh.Parameters["string"] = new Parameter(typeof(string));
//pvh.Parameters["Guid"] = new Parameter(typeof(Guid));
//pvh.Parameters["Convert"] = new Parameter(typeof(Convert));
//pvh.Parameters["Math"] = new Parameter(typeof(Math));
//pvh.Parameters["Array"] = new Parameter(typeof(Array));
//pvh.Parameters["Random"] = new Parameter(typeof(Random));
//pvh.Parameters["TimeZone"] = new Parameter(typeof(TimeZone));
// Add child binding values
for (int i = 0; i < values.Length; i++)
{
IDataDescriptor value = values[i];
Type type = value.DataType;
if (type != null && !pvh.Parameters.Contains(type.Name))
{
pvh.Parameters[type.Name] = new Parameter(type);
}
pvh.Parameters[i.ToString()] = new Parameter(value.Value, type);
}
evaluator.VariableHolder = pvh;
Tree tree = ep.Parse(expression);
result = evaluator.Eval(tree);
return(TypeConverter.Convert(result, targetType, out result));
}
catch (Exception)
{
return(false);
}
}
public static IVariableHolder CreateIVariableHolder01()
{
IVariableHolder variableHolder = new ParameterVariableHolder();
return(variableHolder);
}
public void TestCreateParameterVariableHolder01()
{
ParameterVariableHolder parameterVariableHolder = CreateParameterVariableHolder01();
Assert.IsNotNull(parameterVariableHolder);
}
static void Main(string[] args)
{
Type type = typeof(string);
Parser ep = new Parser();
Evaluater evaluater = new Evaluater();
ParameterVariableHolder pvh = new ParameterVariableHolder();
pvh.Parameters["char"] = new Parameter(typeof(char));
pvh.Parameters["sbyte"] = new Parameter(typeof(sbyte));
pvh.Parameters["byte"] = new Parameter(typeof(byte));
pvh.Parameters["short"] = new Parameter(typeof(short));
pvh.Parameters["ushort"] = new Parameter(typeof(ushort));
pvh.Parameters["int"] = new Parameter(typeof(int));
pvh.Parameters["uint"] = new Parameter(typeof(uint));
pvh.Parameters["long"] = new Parameter(typeof(string));
pvh.Parameters["ulong"] = new Parameter(typeof(ulong));
pvh.Parameters["float"] = new Parameter(typeof(float));
pvh.Parameters["double"] = new Parameter(typeof(double));
pvh.Parameters["decimal"] = new Parameter(typeof(decimal));
pvh.Parameters["DateTime"] = new Parameter(typeof(DateTime));
pvh.Parameters["string"] = new Parameter(typeof(string));
pvh.Parameters["Guid"] = new Parameter(typeof(Guid));
pvh.Parameters["Convert"] = new Parameter(typeof(Convert));
pvh.Parameters["Math"] = new Parameter(typeof(Math));
pvh.Parameters["Array "] = new Parameter(typeof(Array));
pvh.Parameters["Random"] = new Parameter(typeof(Random));
pvh.Parameters["TimeZone"] = new Parameter(typeof(TimeZone));
pvh.Parameters["AppDomain "] = new Parameter(typeof(AppDomain));
pvh.Parameters["Console"] = new Parameter(typeof(Console));
pvh.Parameters["evaluater"] = new Parameter(evaluater);
evaluater.VariableHolder = pvh;
while (true)
{
System.Console.WriteLine("Input line,press Return to Eval:");
string line = System.Console.ReadLine().Trim();
if (string.IsNullOrEmpty(line))
{
break;
}
try
{
Tree tree = ep.Parse(line);
tree.Print(System.Console.Out);
object result = evaluater.Eval(tree);
if (result != null)
{
System.Console.WriteLine("Resut:{0}", result);
}
else
{
System.Console.WriteLine("Resut is null");
}
}
catch (Exception e)
{
System.Console.WriteLine("Exception:" + e.GetType().Name + "->" + e.Message);
}
}
}
public static ParameterVariableHolder CreateParameterVariableHolder01()
{
ParameterVariableHolder parameterVariableHolder = new ParameterVariableHolder();
return(parameterVariableHolder);
}
