小编Mat*_*att的帖子

码:

double cafeSales = db.InvoiceLines
    .Where(x =>
        x.UserId == user.UserId &&
        x.DateCharged >= dateStart &&
        x.DateCharged <= dateEnd)
    .Sum(x => x.Quantity * x.Price);

错误:

转换为值类型"Double"失败,因为实现值为null.结果类型的泛型参数或查询必须使用可空类型.

我已经看到了什么:

转换为值类型"Int32"失败,因为实现值为null

转换为值类型'Decimal'失败,因为具体化值为null

我做了什么:

double cafeSales = db.InvoiceLines
    .Where(x =>
        x.UserId == user.UserId &&
        x.DateCharged >= dateStart &&
        x.DateCharged <= dateEnd)
    .DefaultIfEmpty()
    .Sum(x => x.Quantity * x.Price);

和:

double? cafeSales = db.InvoiceLines
    .Where(x =>
        x.UserId == user.UserId &&
        x.DateCharged >= dateStart &&
        x.DateCharged <= dateEnd)
    .Sum(x => x.Quantity * x.Price);

这些都不奏效.我知道问题的原因是该表中没有我传入的UserId中的行.在这种情况下,我更喜欢Sum()只返回0给我.有任何想法吗？

我正在学习Java,需要运行一些简单的东西,通过JDBC从MSSQL中检索一些数据.我书中的例子不起作用(但它已经有好几年了)以下MS的这个例子对我来说也不起作用:

http://msdn.microsoft.com/en-us/library/ms378956(v=sql.90).aspx

这是我的代码:

package javasql;
import java.sql.*;
import java.util.*;

public class Program {

    private static String url = "jdbc:sqlserver://localhost\\SQLExpress;database=Northwind;integratedSecurity=true;";
    //private static String userName = "sa";
    //private static String password = "myPassword";

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        RunDemo();
    }

    public static void RunDemo() {
        try {
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
            Connection connection = DriverManager.getConnection(url);

            Statement statement = connection.createStatement();
            ResultSet results = statement.executeQuery("SELECT ProductName, Price FROM Products ORDER BY ProductName");

            while(results.next()) {
                System.out.println("Product Name: " …

缓存解决方案和索引解决方案之间的真正区别是什么？在我看来,索引解决方案实际上是具有运行搜索查询的能力(如:弹性搜索).是否有任何真正的理由在同一个项目中同时使用缓存解决方案和索引解决方案,或者索引解决方案是否基本上使任何其他缓存变得多余？

示例:假设我将NEST用于ElasticSearch,它将存储和返回POCO; 如果我然后查询ElasticSearch并将POCO返回给我,是不是认为使用从ElasticSearch返回的缓存对象？

目前,我使用ICacheManager接口将数据存储在缓存中......我是这样的:

return CacheManager.Get(cacheKey, () =>
{
    // return something...
});

ElasticSearch会变得多余吗？

编辑

感谢大家的回答.我完全清楚缓存是什么,并且已经理解了文本搜索索引背后的一般思想,所以我只是想知道索引是否已经兼作缓存,因此会使任何其他缓存变得多余.毕竟,当一个人做得很好时,我不想在内存中保留2个缓存(例如:ElasticSearch + Redis).我想我现在有一个更好的主意; 特别是当我意识到并非所有字段都始终存储在索引中时,因此我们需要从缓存中获取对象或者直接从数据库中获取对象 - 至少在某些情况下是这样.谢谢大家!

我需要创建一个bootstrap手风琴.下面的标记工作正常,但它不会自动折叠以前打开的元素.例如,打开panel1,然后单击panel2 .. panel1应该自动关闭,但它不会.我已经尝试从引导站点(http://twitter.github.com/bootstrap/javascript.html#collapse)完全复制标记,但它无法正常工作.我错过了什么？

<h3>ACCORDION DEMO</h3>
<div class="accordion" id="accordion1">
    <div class="accordion-group">
        <div class="accordion-heading">
            <a class="accordion-toggle" data-parent="accordion1" data-toggle="collapse" href="#panel1">Panel 1</a>
        </div>
        <div class="accordion-body collapse" id="panel1">
            <div class="accordion-inner">
                <p>This is accordion panel 1 content</p>
            </div>
        </div>
    </div>
    <div class="accordion-group">
        <div class="accordion-heading">
            <a class="accordion-toggle" data-parent="accordion1" data-toggle="collapse" href="#panel2">Panel 2</a>
        </div>
        <div class="accordion-body collapse" id="panel2">
            <div class="accordion-inner">
                <p>This is accordion panel 2 content</p>
            </div>
        </div>
    </div>
</div>

我正在使用Twitter Prettify和Twitter Bootstrap.它正在工作,但由于某种原因,行号没有出现.

这是标记:

<pre class="prettyprint linenums">
    <ol class="linenums">
        <li class="L0">
            <span class="kwd">public</span>
            <span class="pln"> </span>
            <span class="kwd">override</span>
            <span class="pln"> </span>
            <span class="kwd">void</span>
            <span class="pln"> </span>
            <span class="typ">Dispose</span>
            <span class="pun">()</span>
        </li>
        <li class="L1">
            <span class="pln"> </span>
            <span class="pun">{</span>
        </li>
        <li class="L2">
            <span class="pln"> </span>
            <span class="kwd">base</span>
            <span class="pun">.</span>
            <span class="typ">Dispose</span>
            <span class="pun">();</span>
        </li>
            <li class="L3">
            <span class="pln"> </span>
            <span class="pun">}</span>
        </li>
    </ol>
</pre>

我称之为:

<script type="text/javascript">
    $(document).ready(function () {
        prettyPrint();
    });
</script>

我没有任何自定义CSS ..只使用Bootstrap CSS ..

我需要建模一个继承自基类泛型类的具体泛型类.首先,见下文:

ActivityFacade应该以这种方式实现:

public class ActivityFacade : BaseFacade<Activity, int>
{
}

如何在VS2012 UML类图中对此进行建模？查看图表,很明显ActivityFacade继承自BaseFacade,但不明显的是它传入的泛型类型参数,即:Activity和int.

试着绕过旧的C语言.目前在结构上并收到此错误:

"variable 'item1' has initializer but incomplete type"

这是我的代码:

typedef struct
{
    int id;
    char name[20];
    float rate;
    int quantity;
} item;

void structsTest(void);

int main()
{
    structsTest();

    system("PAUSE");
    return 0;
}

void structsTest(void)
{
    struct item item1 = { 1, "Item 1", 345.99, 3 };
    struct item item2 = { 2, "Item 2", 35.99, 12 };
    struct item item3 = { 3, "Item 3", 5.99, 7 };

    float total = (item1.quantity * item1.rate) + (item2.quantity * item2.rate) + (item3.quantity …

我试图得到Spring和Quartz的基本示例.以下是我关注的教程:http://www.mkyong.com/spring/spring-quartz-scheduler-example/

我已经完全按照我的意思复制了所有内容,但是在输出窗口中没有看到任何内容.

弹簧quartz.xml

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    <bean id="runMeTask" class="com.ksc.jobs.RunMeTask" />

    <!-- Spring Quartz -->
    <bean name="runMeJob" class="org.springframework.scheduling.quartz.JobDetailBean">
        <property name="jobClass" value="com.ksc.jobs.RunMeJob" />
        <property name="jobDataAsMap">
            <map>
                <entry key="runMeTask" value-ref="runMeTask" />
            </map>
        </property>

    </bean>

    <bean id="simpleTrigger" class="org.springframework.scheduling.quartz.SimpleTriggerBean">
        <property name="jobDetail" ref="runMeJob" />
        <property name="repeatInterval" value="5000" />
        <property name="startDelay" value="1000" />

    </bean>

    <bean class="org.springframework.scheduling.quartz.SchedulerFactoryBean">
        <property name="jobDetails">
            <list>
                <ref bean="runMeJob" />
            </list>
        </property>

        <property name="triggers">
            <list>
                <ref bean="simpleTrigger" />
            </list>
        </property>
    </bean>

</beans>

applicationContext.xml中

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" 
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans …

我正在使用jtDS JDBC驱动程序,当我调用时,ResultSet.getNString(index);我得到以下异常:

run:
Exception in thread "main" java.lang.AbstractMethodError: net.sourceforge.jtds.jdbc.JtdsResultSet.getNString(I)Ljava/lang/String;
    at javasql.ProductsController.PrePopulate(ProductsController.java:51)
    at javasql.ProductsController.<init>(ProductsController.java:37)
    at javasql.Program.main(Program.java:25)
Java Result: 1
BUILD SUCCESSFUL (total time: 6 seconds)

当我使用getString(index)它工作正常..它只是getNString()因为我有一个问题,我的MSSQL表中的列被定义为NVarChar.那么,是什么给出的？jtDS不支持getNString()吗？也许它得到了两个VarChar并NVarChar通过相同的getString()功能？

编辑:

相关的unicode问题..我可以看到尝试使用Unicode无法插入任何一个.我的列被定义为nvarchar(255),但以下INSERT语句不起作用:

private final String INSERT_FORMAT = "INSERT INTO Products (Name, Price, QuantityInStock) VALUES (N'%s', %s, %s)";

    public void Insert(Product p) {
            products.add(p);
            try {
                statement.addBatch(String.format(INSERT_FORMAT, p.getName(), p.getPrice(), p.getQuantityInStock()));
            } catch (SQLException ex) {
                System.out.println(ex.getMessage()); …

试图从OData v3迁移到OData v4.为什么我在尝试使用OData函数时会继续获得404？

Web API配置:

ODataModelBuilder builder = new ODataConventionModelBuilder();
//etc
builder.EntitySet<LocalizableString>("LocalizableStringApi");
//etc
var getComparitiveTableFunction = builder.EntityType<LocalizableString>().Collection.Function("GetComparitiveTable");
getComparitiveTableFunction.Parameter<string>("cultureCode");
getComparitiveTableFunction.ReturnsCollection<ComparitiveLocalizableString>();
//etc
config.MapODataServiceRoute("OData_Kore_CMS", "odata/kore/cms", builder.GetEdmModel());

C#代码:

[EnableQuery(AllowedQueryOptions = AllowedQueryOptions.All)]
[HttpGet]
//[ODataRoute("Default.GetComparitiveTable(cultureCode={cultureCode})")] // Tried this, but gets errors and I noticed the function is in the OData model anyway without this, so should be fine.
public virtual IHttpActionResult GetComparitiveTable([FromODataUri] string cultureCode)
{
    // Implementation
    return Ok(query);
}

从$ metadata返回的XML:

<Schema Namespace="Default">
    <Function Name="GetComparitiveTable" IsBound="true">
        <Parameter …