我有以下扩展方法,使字符串能够做到这一点("true").As<bool>(false)
特别是对于布尔值,它将用于AsBool()做一些自定义转换.不知怎的,我不能从T转向Bool,反之亦然.我使用下面的代码工作,但它似乎有点矫枉过正.
这是关于这一行:
(T)Convert.ChangeType(AsBool(value, Convert.ToBoolean(fallbackValue)), typeof(T))
我宁愿使用以下内容,但它不会编译:
(T)AsBool(value, (bool)fallbackValue), typeof(T))
我错过了什么或者这是最短的路要走？
public static T As<T>(this string value)
{
return As<T>(value, default(T));
}
public static T As<T>(this string value, T fallbackValue)
{
if (typeof(T) == typeof(bool))
{
return (T)Convert.ChangeType(AsBool(value,
Convert.ToBoolean(fallbackValue)),
typeof(T));
}
T result = default(T);
if (String.IsNullOrEmpty(value))
return fallbackValue;
try
{
var underlyingType = Nullable.GetUnderlyingType(typeof(T));
if (underlyingType == null)
result = (T)Convert.ChangeType(value, typeof(T));
else if (underlyingType == typeof(bool))
result = (T)Convert.ChangeType(AsBool(value,
Convert.ToBoolean(fallbackValue)),
typeof(T));
else
result = (T)Convert.ChangeType(value, …我已经设置了一个VirtualPathProvider,它可以正常工作,如http://.../home/index地址栏中的直接网址调用.
public class HomeController
{
public ActionResult Index()
{
// This triggers MyVirtualPathProvider functionallity when called via
// the browsers address bar or anchor tag click for that matter.
// But it does not trigger MyVirtualPathProvider for 'in-view' calls like
// @{ Html.RenderAction("index", "home"); }
return View();
}
}
public class MyVirtualPathProvider : VirtualPathProvider
{
public override System.Web.Hosting.VirtualFile GetFile(string virtualPath)
{
// This method gets hit after the Controller call for return View(...);
if (MyCondition)
return …我正在使用Silverlight 5构建一个3D应用程序.我有一个调用方法的DrawingSurface.但是,当我向我的XAML添加导航:Frame时,我会抛出一个错误.
这是有问题的方法:
private void DrawingSurface_Draw(object sender, DrawEventArgs e)
{
GraphicsDevice device = GraphicsDeviceManager.Current.GraphicsDevice;
device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer,
new Microsoft.Xna.Framework.Color(0, 0, 0, 0), 10.0f, 0);
device.SetVertexBuffer(_vertexBuffer);
device.SetVertexShader(_vertexShader);
device.SetPixelShader(_pixelShader);
device.Textures[0] = _texture;
device.SamplerStates[0] = SamplerState.LinearClamp;
device.DrawPrimitives(PrimitiveType.TriangleList, 0,
_vertexBuffer.VertexCount / 3);
device.SetVertexShaderConstantFloat4(0, ref _viewProjection);
e.InvalidateSurface();
}
错误在线device.DrawPrimitives(PrimitiveType.TriangleList, 0, _vertexBuffer.VertexCount / 3);.错误是"NullReferenceException未被用户代码处理".没有导航就不会发生:框架.
我使用 linq join 组合了我的 3 个表。之后，我想使用从 webform 获取的数据更新此表。我怎样才能做到这一点 ？我的实现如下
public void updateShoes(Shoe shoe)
{
var query = from b in db.BrandTbls.AsQueryable()
join m in db.ShoeModelTbls on b.BrandID equals m.BrandID
join s in db.ShoeTbls on m.ModelID equals s.ModelID
where shoe.ShoeID == s.ShoeID
orderby m.ModelName
select new
{
s.ShoeID,
s.Size,
s.PrimaryColor,
s.SecondaryColor,
s.Quantity,
m.ModelName,
m.Price,
b.BrandName
};
}
我意识到有数百页与此错误相关。然而，我已经查看了其中的许多内容，但无法找到与我的特定问题相关的内容，因此，如果这是重复的线程，我深表歉意。我正在尝试修改 Unity 提供的 2D 相机脚本，以将其“目标”（它遵循的游戏对象）选择为用户选择的任何角色。我是 C# 新手，所以我不太清楚如何处理这个错误。我发布了整个代码以防万一，但错误应该可以在前 10 行左右找到
using UnityEngine;
namespace UnitySampleAssets._2D
{
public class Camera2DFollow : MonoBehaviour
{
private string character = PlayerPrefs.GetString("Character")
public Transform target = Transform.Find(character);
public float damping = 1;
public float lookAheadFactor = 3;
public float lookAheadReturnSpeed = 0.5f;
public float lookAheadMoveThreshold = 0.1f;
private float offsetZ;
private Vector3 lastTargetPosition;
private Vector3 currentVelocity;
private Vector3 lookAheadPos;
// Use this for initialization
private void Start()
{
lastTargetPosition = target.position;
offsetZ = (transform.position - target.position).z;
transform.parent …