public static Expression<Func<T, bool>> True<T>() { return f => true; }
public static Expression<Func<T, bool>> False<T>() { return f => false; }
/// <summary>
/// 条件或
/// </summary>
/// <typeparam name=”T”></typeparam>
/// <param name=”expr1″></param>
/// <param name=”expr2″></param>
/// <returns></returns>
public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2) {
var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>> (Expression.Or(expr1.Body, invokedExpr), expr1.Parameters);
}
/// <summary>
/// 条件且
/// </summary>
/// <typeparam name=”T”></typeparam>
/// <param name=”expr1″></param>
/// <param name=”expr2″></param>
/// <returns></returns>
public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2) {
var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>>
(Expression.And(expr1.Body, invokedExpr), expr1.Parameters);
}
