/// <summary>
/// 将两个Lamda表达式构建“or”的连接关系
/// </summary>
/// <typeparam name="T">实体类</typeparam>
/// <param name="exp_left">“or”的左端Lamda表达式</param>
/// <param name="exp_right">“or”的右端Lamda表达式</param>
/// <returns>Lamda表达式</returns>
public static Expression <Func <T, bool> > Or <T>(this Expression <Func <T, bool> > exp_left, Expression <Func <T, bool> > exp_right)
{
var candidateExpr = Expression.Parameter(typeof(T), "candidate");
var parameterReplacer = new ParameterReplacer(candidateExpr);
var left = parameterReplacer.Replace(exp_left.Body);
var right = parameterReplacer.Replace(exp_right.Body);
var body = Expression.Or(left, right);
// 创建一个表示“OR”关系的Lamda表达式
return(Expression.Lambda <Func <T, bool> >(body, candidateExpr));
}
/// <summary>
/// 将两个Lamda表达式构建“and”的连接关系
/// </summary>
/// <typeparam name="T">实体类</typeparam>
/// <param name="exp_left">“and”的左端Lamda表达式</param>
/// <param name="exp_right">“and”的右端Lamda表达式</param>
/// <returns>Lamda表达式</returns>
public static Expression <Func <T, bool> > And <T>(this Expression <Func <T, bool> > exp_left, Expression <Func <T, bool> > exp_right)
{
var candidateExpr = Expression.Parameter(typeof(T), "candidate");
var parameterReplacer = new ParameterReplacer(candidateExpr);
var left = parameterReplacer.Replace(exp_left.Body); // 获取Lamda表达式的主体
var right = parameterReplacer.Replace(exp_right.Body); // 获取Lamda表达式的主体
// 创建按位AND运算的二进制Lamda表达式
var body = Expression.And(left, right);
// 创建一个表示“AND”关系的Lamda表达式
return(Expression.Lambda <Func <T, bool> >(body, candidateExpr));
}