小编Joh*_*arr的帖子

所以,我收到了标题中的错误.我将直接进入相关代码.首先,手动创建where语句(确实有效),然后动态创建不起作用.两者都创建相同的queryExpression.

首先,使用两种方法生成的queryExpression:

{Table(Products).Select
  (s => new SalesData() {
    ProductID = s.ProductID,
    StoreName = s.StoreName, 
    Count = s.Count
}).Where(s => (s.Count > 500))}

现在,工作的手动方法:

IQueryable<SalesData> data = ( from s in sales.Products
                               select new SalesData
                               {
                                   ProductID = s.ProductID,
                                   StoreName = s.StoreName,
                                   Count = s.Count
                               } ).AsQueryable<SalesData>();

data = data.Where(s => s.Count > 500);

this.dataGridView1.DataSource = null;

this.dataGridView1.DataSource = (from d in data
                                 select new
                                 {
                                     d.ProductID,
                                     d.StoreName,
                                     d.Count
                                 } );

这按预期工作; 我的DataGridView填充了数据.

现在,动态创建where子句:

IQueryable<SalesData> data = ( from s in …

我已经使用了Entity Framework已经有一段时间了,我正在重新使用EF 5,但不会这个查询:

SELECT 
    c.OrganizationName as CompanyName,
    c.OrganizationKey as CompanyId,
    ISNULL(a.Line1, '') as Line1,
    ISNULL(a.Line2, '') as Line2,
    a._CityStateZip as CityStateZip
FROM Organizations c
JOIN Addresses a ON c.AddressKey = a.AddressKey
WHERE c.OrganizationName LIKE @term + '%'
AND c.IsSuspended = 0
AND c.IsActive = 1

与以下相同:

var results = (from c in adms.Organizations
               where c.OrganizationName.StartsWith(term)
               where !c.IsSuspended
               where c.IsActive
               select new
               {
                 CompanyName = c.OrganizationName,
                 CompanyId = c.OrganizationKey,
                 Line1 = (string.IsNullOrEmpty(c.Address.Line1) ? string.Empty : c.Address.Line1),
                 Line2 = (string.IsNullOrEmpty(c.Address.Line2) ? string.Empty …

我正在使用Entity Framework学习ASP.Net MVC.我想得到最后保存记录的ID.我已经检查了这个,当你想获得最近保存的记录的id时,接受的答案正常.我需要两天前可能保存的记录.

我该如何检索？

任何人都可以提供任何想法,为什么我的空检查评估错误？

还应该指出,如果我不为空,则评估是正确的.我不确定还有什么相关内容,但让我知道我需要提供的其他细节.

foreach (var item in selectedItems)
{
    var i = inspectionItems.Keys.SingleOrDefault(x => x.InspectionItemId == item.InspectionItemId);
    if (i != null)
    {
        // Process i
     }
     else
     {
       // create
     }
}

为什么以下每个都返回记录:

SELECT Name, CreatedDate 
FROM EmployeeTable 
WHERE CreatedDate < '20151214'

SELECT Name, CreatedDate 
FROM EmployeeTable 
WHERE CreatedDate > '20151214'

虽然以下查询没有？

SELECT Name, CreatedDate 
FROM EmployeeTable 
WHERE CreatedDate = '20151214'

我必须使用CAST带有相等运算符的a来获得我想要的结果:

SELECT Name, CreatedDate 
FROM EmployeeTable 
WHERE CAST(CreatedDate as DATE) = '2015-12-14'

有没有办法使用相等运算符而不必使用强制转换？

CreatedDate是类型DATETIME,包括时间.

我想WHERE只在变量有数据的情况下为子句添加一个条件.

我尝试使用以下case语句,但它有语法错误.

Declare @last_name varchar(10) = null;
Select * from TABLE1 
Where FirstName = 'John'
AND CASE WHEN @last_name IS NOT NULL THEN LastName = @last_name