[英]Dynamic query in linq or lambda expression C#
我需要根据用户输入构造一个动态查询。
我曾经使用带字符串连接的SqlCommand
来做到这一点。
例:
public ActionResult Receipt_Details(string FromDate, string ToDate, int Branch, int User, int RecietType, int PayMethod)
{
if (FromDate == "")
FromDate = "1980-01-01";
if (ToDate == "")
ToDate = "2180-01-01";
string where = " where DmentDate>='"+FromDate+ "' and DmentDate<='"+ToDate +"'";
if (Branch != 0) // Branch = 0 means select all branches
where += " and BranchID = " + Branch;
if (User != 0) // User = 0 means select all users
where += " and UserID = " + User
if (PayMethod != 0)
where += " and PayMethodID = " + PayMethod
string constr = "data source=.;initial catalog=db;integrated security=True;";
using (SqlConnection con = new SqlConnection (constr))
{
con.Open();
using (SqlCommand com=new SqlCommand())
{
com.Connection = con;
com.command="Select * from Table "+ where;
}
}
}
现在,我使用实体框架。 我想使用类和linq或lambda表达式
谢谢
如果要将这种方法重构为使用EF和LINQ的解决方案,则其工作方式基本上相同。
//query will be of type IQueryable<T>
var query = context.Receipts;
//modify the query based on your needs
if(Branch != 0)
query = query.Where(x => x.Branch == Branch);
if (User!=0)
query = query.Where(x => x.UserId == User);
/* ... and so on */
//execute
return query.ToList() // materialize your query with ToList or FirstOrDefault() or whatever you need.
提醒一下,将日期视为字符串是灾难的征兆。 日期可以强类型化为DateTime
。
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