public static Expression <Func <T, bool> > Or <T>(
this Expression <Func <T, bool> > one, Expression <Func <T, bool> > another)
{
var candidateExpr = Expression.Parameter(typeof(T), "candidate");
var parameterReplacer = new ParameterReplacer(candidateExpr);
var left = parameterReplacer.Replace(one.Body);
var right = parameterReplacer.Replace(another.Body);
var body = Expression.Or(left, right);
return(Expression.Lambda <Func <T, bool> >(body, candidateExpr));
}
public static Expression <Func <T, bool> > And <T>(this Expression <Func <T, bool> > one,
Expression <Func <T, bool> > another)
{
// 首先定义好一个ParameterExpression
var candidateExpr = Expression.Parameter(typeof(T), "candidate");
var parameterReplacer = new ParameterReplacer(candidateExpr);
// 将表达式树的参数统一替换成我们定义好的candidateExpr (表达式分为 参数和body，将参数统一成一个对象)
var left = parameterReplacer.Replace(one.Body);
var right = parameterReplacer.Replace(another.Body);
var body = Expression.And(left, right);
return(Expression.Lambda <Func <T, bool> >(body, candidateExpr));
}