我知道Null Reference异常总是模糊不清，任何数量的东西都可以产生它但我在这里的想法已经用完了......发生的事情是当我尝试点击食谱类别链接时我得到这个错误：
NullReferenceException: Object reference not set to an instance of an object.
Company.BusinessLayer.Recipes.SearchManager.GetRecipes(Int64 folderId, String searchTerm, Int32 pageIndex, Int32 pageSize, Int32& categoryCount, Int32& pageCount) +1020
TargetInvocationException: Exception has been thrown by the target of an invocation.
Comapny.Website.Controls.Recipes.CategoryControl.ods_Selected(Object sender, ObjectDataSourceStatusEventArgs e) +940
System.Web.UI.WebControls.ObjectDataSourceView.OnSelected(ObjectDataSourceStatusEventArgs e) +103
System.Web.UI.WebControls.ObjectDataSourceView.InvokeMethod(ObjectDataSourceMethod method, Boolean disposeInstance, Object& instance) +431
System.Web.UI.WebControls.ObjectDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments) +1953
System.Web.UI.WebControls.BaseDataList.GetData() +56
System.Web.UI.WebControls.DataList.CreateControlHierarchy(Boolean useDataSource) +177
System.Web.UI.WebControls.BaseDataList.OnDataBinding(EventArgs e) +64
System.Web.UI.WebControls.BaseDataList.DataBind() +55
Company.Website.Controls.Recipes.CategoryControl.OnPreRender(EventArgs e) +138
System.Web.UI.Control.PreRenderRecursiveInternal() +103
System.Web.UI.Control.PreRenderRecursiveInternal() +175
System.Web.UI.Control.PreRenderRecursiveInternal() +175
System.Web.UI.Control.PreRenderRecursiveInternal() +175
System.Web.UI.Control.PreRenderRecursiveInternal() +175
System.Web.UI.Control.PreRenderRecursiveInternal() +175
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2496
我无法弄清楚什么是被处理为null。这是来自SearchManager.cs的代码和错误消息引用的GetRecipes方法。数据全部存储在数据库中，不应该为null。在升级此项目依赖的程序集之前，它正在工作。唯一改变的是程序集使用int64而不是int，但为了得到该死的项目，我必须将它们转换为int。尽管在这种情况下我会想到并不重要。我不知道我在这里抓住空气。
public ContentBase[] GetRecipes(long folderId, string searchTerm, int pageIndex, int pageSize, out int categoryCount, out int pageCount)
{
ContentBase[] mergedResultset = null;
IndexSearch idx = new IndexSearch();
idx.XmlConfigId = 8;
idx.FolderId = folderId;
idx.Recursive = true;
// if a search term is provided, search this term
if (!string.IsNullOrEmpty(searchTerm))
{
searchTerm = searchTerm.Replace("'", "''");
// INDEX SEARCH BASED ON INGREDIENTS
Ektron.Cms.Controls.IndexSearch.SearchPram paramTerm = new Ektron.Cms.Controls.IndexSearch.SearchPram();
paramTerm.DataType = Ektron.Cms.Common.EkEnumeration.XMLDataType.String;
paramTerm.SearchType = Ektron.Cms.Common.EkEnumeration.XMLSearchRangeType.Contains;
paramTerm.XPath = "/root/Ingredients";
paramTerm.Value1 = searchTerm;
idx.AddParm(paramTerm);
idx.Search();
mergedResultset = (ContentBase[])idx.EkItems;
// CUSTOM SEARCH BASED ON TITLE
FolderData[] childFolders = GetChildFolders(folderId, true);
// Search based on title
Ektron.Cms.API.Search.SearchManager search = new Ektron.Cms.API.Search.SearchManager();
Ektron.Cms.ContentSearchCondition conditionAll = new Ektron.Cms.ContentSearchCondition();
conditionAll.setType = EkEnumeration.SearchType.AND;
ContentSearchCondition condFolderIds = new ContentSearchCondition();
// add condition folder Id for current folder and for each sub folder
condFolderIds.setType = EkEnumeration.SearchType.OR;
AddFolderIdCondition(condFolderIds, folderId);
foreach (FolderData fd in childFolders)
{
AddFolderIdCondition(condFolderIds, fd.Id);
}
conditionAll.AddCondition(condFolderIds);
ContentSearchCondition condTerm = new ContentSearchCondition();
condTerm.setType = EkEnumeration.SearchType.LIKE;
condTerm.setValue = searchTerm;
condTerm.setVariable = "content.content_title";
conditionAll.AddCondition(condTerm);
ContentSearchCondition condType = new ContentSearchCondition();
condType.setType = EkEnumeration.SearchType.EQUAL;
condType.setValue = 8;
condType.setVariable = "content.xml_config_id";
conditionAll.AddCondition(condType);
ContentData[] contents = search.Execute(conditionAll);
mergedResultset = MergeResultsets(idx.EkItems, contents, "/Recipes/Detail.aspx");
// rewrite all quicklinks with url alias
IDictionary<int, string> aliases = new UrlAliasApi().GetUrlAliasesByType(Company.DataLayer.Enumeration.UrlAliasType.Recipe);
foreach (ContentBase recipe in mergedResultset)
{
// if alias exists, overwrite quicklink!
string alias;
if (aliases.TryGetValue((int)recipe.Id, out alias))
{
recipe.QuickLink = alias;
}
}
}
// otherwise search based without parameter (fake param)
else
{
// if category recipes not already in cache, get them through ektron, otherwise, just get them from cache
if (RecipeCategoryCache.Current.Categories.ContainsKey((int)folderId) && RecipeCategoryCache.Current.Categories[(int)folderId] != null && RecipeCategoryCache.Current.Categories[(int)folderId].Length > 0)
{
mergedResultset = RecipeCategoryCache.Current.Categories[(int)folderId];
}
else
{
Ektron.Cms.Controls.IndexSearch.SearchPram param = new Ektron.Cms.Controls.IndexSearch.SearchPram();
param.DataType = Ektron.Cms.Common.EkEnumeration.XMLDataType.Boolean;
param.SearchType = Ektron.Cms.Common.EkEnumeration.XMLSearchRangeType.True;
param.XPath = "/root/Viewable";
idx.AddParm(param);
idx.Search();
mergedResultset = (ContentBase[])idx.EkItems;
// rewrite all quicklinks with url alias
IDictionary<int, string> aliases = new UrlAliasApi().GetUrlAliasesByType(Company.DataLayer.Enumeration.UrlAliasType.Recipe);
foreach (ContentBase recipe in mergedResultset)
{
// if alias exists, overwrite quicklink!
string alias;
if (aliases.TryGetValue((int)recipe.Id, out alias))
{
recipe.QuickLink = alias;
}
}
RecipeCategoryCache.Current.Categories[(int)folderId] = mergedResultset;
}
}
categoryCount = mergedResultset.Length;
// if page size provided is 0, No paging,
// if more than 0, calculate paging
if (pageSize > 0 && mergedResultset.Length > 0)
{
PagingHelper pgHelper = new PagingHelper();
pgHelper.CalculatePagingInfo(pageIndex, categoryCount, pageSize);
pageCount = pgHelper.NumberOfPages;
List<ContentBase> lst = new List<ContentBase>();
for (int i = pgHelper.StartIndex; i < pgHelper.EndIndex; i++)
{
lst.Add(mergedResultset[i]);
}
return lst.ToArray();
}
else
{
pageCount = 1;
return mergedResultset;
}
}
答案 0 :(得分：1)
您需要添加TON的错误处理代码。 “if（x == null）”类型的语句没有单个“if（x！= null）”。你需要重写所有代码才能更具防御性。
是的，要找到这个特定的错误，你需要逐步完成你的程序。并看看它在哪里爆炸。但是如果你解决了这个问题，除非你添加了很多错误检查代码，否则无法保证你的代码在5分钟后不会在其他地方爆炸。
看起来你在这个方法中调用外部代码。基本上，您需要验证从中获得的所有内容，看起来您信任外部代码以始终返回有效数据。
答案 1 :(得分：0)
为什么不在函数顶部设置一个中断并逐步调试并检查变量？这是找出空引用异常的原因的最简单方法。
答案 2 :(得分：0)
没有在那里并且能够深入研究你的代码，这几乎是不可能的。我可以告诉你要做的是查找null的子对象。例如，假设你有一个Car对象：
class Car(){
string Color;
string Make;
string Model;
Passenger passenger; // Passenger is a another object defined elsewhere
}
在代码中的某些时候，你会做类似的事情......
Car car = new Car（）;
然后你去某个地方使用它，在你的代码中，有些东西试图访问Passenger的属性，但Passenger是NULL。问题是，在更高的层次上，当你看到汽车时，你会发现汽车不是空的，所以你认为它没问题。理解？
所以......检查你的复杂对象是否为空，看看它到底在哪里。顺便说一句，如果你尝试在你的代码中使用广泛定义的语句，那么它们就会导致这种错误并使其难以找到......