/// <summary>
/// 匹配一种规则
/// </summary>
public static Func <T, bool> CompileRule <T>(RuleModule r)
{
var paramUser = Expression.Parameter(typeof(T));
Expression expr = BuildExpr <T>(r, paramUser);
return(Expression.Lambda <Func <T, bool> >(expr, paramUser).Compile());
}
/// <summary>
/// 匹配两种规则
/// </summary>
public static Func <T, bool> CompileRule <T>(RuleModule leftrule, RuleModule rightrule)
{
var paramUser = Expression.Parameter(typeof(T));
Expression leftexpr = BuildExpr <T>(leftrule, paramUser);
Expression rightexpr = BuildExpr <T>(rightrule, paramUser);
Expression express = Expression.AndAlso(leftexpr, rightexpr);
return(Expression.Lambda <Func <T, bool> >(express, paramUser).Compile());
}
/// <summary>
/// 构建lambra表达式树
/// </summary>
private static Expression BuildExpr <T>(RuleModule r, ParameterExpression param)
{
var left = MemberExpression.Property(param, r.MemberName);
var tProp = typeof(T).GetProperty(r.MemberName).PropertyType;
ExpressionType tBinary;
if (ExpressionType.TryParse(r.Operator, out tBinary))
{
var right = Expression.Constant(Convert.ChangeType(r.TargetValue, tProp));
return(Expression.MakeBinary(tBinary, left, right));
}
else
{
var method = tProp.GetMethod(r.Operator);
var tParam = method.GetParameters()[0].ParameterType;
var right = Expression.Constant(Convert.ChangeType(r.TargetValue, tParam));
return(Expression.Call(left, method, right));
}
}
