问题描述
我使用the instructions here从而将`变成了快捷方式：
function reset_shortcut_key(e) {
if (e.keyCode == 192) reset_data();
}
document.addEventListener('keyup',reset_shortcut_key,false);
它成功加载了下一个问题，但是当我专注于<form> <input> </form>环境时按下此热键时，`字符会短暂出现（在加载下一个问题之前）。
我想阻止它显示`字符。
问题：如何防止将热键`添加到表单输入中？
其他相关问题是How can I prevent \ from being added from the form input?（但这是关于斜杠的删除）和Javascript -> Hotkeys -> Disable for input fields（和here）（但我希望热键可以正常工作）。
编辑：从当前的评论和答案来看，适当的功能是event.preventDefault()。我仍然不清楚如何实际实现这一点。
仅在document.addEventListener('keyup',false);之前或之后添加它不会执行任何操作。除此之外，
document.addEventListener("keyup",function(event) {
event.preventDefault();
reset_shortcut_key();
},false);
和
document.querySelector("#input-guess").addEventListener("keyup",false);
（其中id="input-guess"是我的<input>的名称）都阻止了reset_shortcut_key()被调用。如下修改reset_shortcut_key不会有任何改变：
function reset_shortcut_key(e) {
e.preventDefault();
if(e.keyCode == 192) reset_data();
}
在这一点上，我只是在猜测该怎么做。
解决方法
您尝试过吗？ https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault
event.preventDefault();
原来，还有第二个问题：我需要使用internal（而不是InternalQuery()）。进行更改后，以下代码（使用using System;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;
using Microsoft.EntityFrameworkCore.Query;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
namespace IssueConsoleTemplate
{
#region Models
public class User
{
public int Id { get; private set; }
public virtual UserProfilePhoto UserProfilePhoto { get; set; }
public static User Create(byte[] profilePhoto)
{
var user = new User
{
UserProfilePhoto = new UserProfilePhoto(profilePhoto)
};
return user;
}
}
public class UserProfilePhoto : INonRootQueryable
{
public int Id { get; set; }
public byte[] ProfilePhoto { get; private set; }
public UserProfilePhoto(byte[] profilePhoto)
{
ProfilePhoto = profilePhoto;
}
}
#endregion
#region Custom implementations
public interface INonRootQueryable
{
}
public class CustomQueryTranslationPreprocessorFactory : IQueryTranslationPreprocessorFactory
{
private readonly QueryTranslationPreprocessorDependencies _dependencies;
private readonly RelationalQueryTranslationPreprocessorDependencies _relationalDependencies;
public CustomQueryTranslationPreprocessorFactory(
QueryTranslationPreprocessorDependencies dependencies,RelationalQueryTranslationPreprocessorDependencies relationalDependencies)
{
_dependencies = dependencies;
_relationalDependencies = relationalDependencies;
}
public virtual QueryTranslationPreprocessor Create(QueryCompilationContext queryCompilationContext)
=> new CustomQueryTranslationPreprocessor(
_dependencies,_relationalDependencies,queryCompilationContext);
}
public class CustomQueryTranslationPreprocessor : RelationalQueryTranslationPreprocessor
{
public CustomQueryTranslationPreprocessor(
QueryTranslationPreprocessorDependencies dependencies,RelationalQueryTranslationPreprocessorDependencies relationalDependencies,QueryCompilationContext queryCompilationContext)
: base(dependencies,relationalDependencies,queryCompilationContext)
{
}
public override Expression Process(Expression query)
{
query = new ThrowOnNoneRootQueryableViolationExpressionVisitor().Visit(query);
return base.Process(query);
}
}
public class ThrowOnNoneRootQueryableViolationExpressionVisitor : ExpressionVisitor
{
private bool _isInternalQuery;
protected override Expression VisitMethodCall(MethodCallExpression node)
{
if (node.Method.GetGenericMethodDefinition() == CustomQueryableExtensions.InternalQueryMethodInfo)
{
_isInternalQuery = true;
return node.Arguments[0];
}
return base.VisitMethodCall(node);
}
protected override Expression VisitConstant(ConstantExpression node)
{
var expression = base.VisitConstant(node);
// Throws if SomeEntity in a DbSet<SomeEntity> implements INonRootQueryable and the query was not chained
// to the `InternalQuery()` extension method.
return !_isInternalQuery &&
node.Type.IsGenericType &&
node.Type.GetGenericTypeDefinition() == typeof(Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable<>) &&
node.Type.GenericTypeArguments.Length == 1 &&
typeof(INonRootQueryable).IsAssignableFrom(node.Type.GenericTypeArguments[0])
? throw new InvalidOperationException($"Directly querying for '{node.Type.Name}' is prohibited.")
: expression;
}
}
internal static class CustomQueryableExtensions
{
internal static readonly MethodInfo InternalQueryMethodInfo
= typeof(CustomQueryableExtensions)
.GetTypeInfo()
.GetDeclaredMethods(nameof(InternalQuery))
.Single(m => m.GetParameters().Length == 1 &&
m.GetParameters()[0].ParameterType.Namespace == $"{nameof(System)}.{nameof(System.Linq)}" &&
m.GetParameters()[0].ParameterType.Name.StartsWith(nameof(IQueryable)) &&
m.GetParameters()[0].ParameterType.GenericTypeArguments.Length == 1);
internal static IQueryable<TSource> InternalQuery<TSource>(this IQueryable<TSource> source)
=> source.Provider.CreateQuery<TSource>(
Expression.Call(
null,InternalQueryMethodInfo.MakeGenericMethod(typeof(TSource)),source.Expression));
internal static IQueryable<TProperty> InternalQuery<TEntity,TProperty>(this ReferenceEntry<TEntity,TProperty> source)
where TEntity : class
where TProperty : class
=> source.Query()
.InternalQuery();
}
#endregion
public class ModelContext : DbContext
{
public DbSet<User> Users { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
// Register the custom type IQueryTranslationPreprocessorFactory.
// Since this is a console program,we need to create our own ServiceCollection
// for this.
// In an ASP.NET Core application,the AddSingleton call can just be added to
// the general service configuration method.
var serviceProvider = new ServiceCollection()
.AddEntityFrameworkSqlServer()
.AddSingleton<IQueryTranslationPreprocessorFactory,CustomQueryTranslationPreprocessorFactory>()
.AddScoped(
s => LoggerFactory.Create(
b => b
.AddConsole()
.AddFilter(level => level >= LogLevel.Information)))
.BuildServiceProvider();
optionsBuilder
.UseInternalServiceProvider(serviceProvider) // <-- use our ServiceProvider
.UseSqlServer(@"Data Source=.\MSSQL14;Integrated Security=SSPI;Initial Catalog=So63887500_05")
.EnableSensitiveDataLogging()
.EnableDetailedErrors();
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
OnUserModelCreating(modelBuilder);
}
protected void OnUserModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<User>(
entity =>
{
entity.HasOne(e => e.UserProfilePhoto)
.WithOne()
.HasForeignKey<UserProfilePhoto>(e => e.Id);
});
}
}
internal static class Program
{
private static void Main()
{
var accessingSetThrows = false;
using (var ctx = new ModelContext())
{
ctx.Database.EnsureDeleted();
ctx.Database.EnsureCreated();
var user = User.Create(new byte[] { });
ctx.Users.Add(user);
ctx.SaveChanges();
}
// Make sure,that UserProfilePhoto cannot be queried directly by default.
using (var ctx = new ModelContext())
{
try
{
ctx.Set<UserProfilePhoto>()
.ToList();
}
catch (InvalidOperationException)
{
accessingSetThrows = true;
}
Debug.Assert(accessingSetThrows);
}
// Make sure,that UserProfilePhoto can be queried directly,when using the `InternalQuery()` extension
// method.
using (var ctx = new ModelContext())
{
var userProfilePhotos = ctx.Set<UserProfilePhoto>()
.InternalQuery()
.ToList();
Debug.Assert(userProfilePhotos.Count == 1);
}
// No eager loading of referenced types by default.
using (var ctx = new ModelContext())
{
var users = ctx.Users.ToList();
Debug.Assert(users.Count == 1);
Debug.Assert(users[0].UserProfilePhoto == null);
}
// Eager loading of referenced types is allowed,when using the `InternalQuery()` extension method.
using (var ctx = new ModelContext())
{
var users = ctx.Users
.Include(u => u.UserProfilePhoto)
.InternalQuery()
.ToList();
Debug.Assert(users.Count == 1);
Debug.Assert(users[0].UserProfilePhoto != null);
}
// Explicitly load profile photo,when using the `InternalQuery()` extension method.
using (var ctx = new ModelContext())
{
var users = ctx.Users.ToList();
ctx.Entry(users[0])
.Reference(u => u.UserProfilePhoto)
.InternalQuery()
.Load();
Debug.Assert(users.Count == 1);
Debug.Assert(users[0].UserProfilePhoto != null);
}
}
}
}
）有效：
keydown