LINQ到实体无​​法识别方法'System.String get_Item（System.String）“， [英] LINQ to Entities does not recognize the method 'System.String get_Item (System.String)',

问题描述

我该如何解决这个问题呢？

How can I solve this problem?

下面是我的code：

    DateTime dtInicio = new DateTime();
    DateTime dtFim = new DateTime();
    Int32 codStatus = 0;

    if(!string.IsNullOrEmpty(collection["txtDtInicial"]))
        dtInicio = Convert.ToDateTime(collection["txtDtInicial"]);
    if(!string.IsNullOrEmpty(collection["txtDtFinal"]))
        dtFim = Convert.ToDateTime(collection["txtDtFinal"]);
    if (!string.IsNullOrEmpty(collection["StatusCliente"]))
        Convert.ToInt32(collection["StatusCliente"]);

    var listCLientResult = (from c in db.tbClientes
                           orderby c.id
                            where (c.effdt >= dtInicio || string.IsNullOrEmpty(collection["txtDtInicial"]) &&
                                 (c.effdt <= dtFim || string.IsNullOrEmpty(collection["txtDtFinal"])) &&
                                 (c.cod_status_viagem == codStatus || string.IsNullOrEmpty(collection["StatusCliente"])))
                                 select c);
    return View(listCLientResult);

我得到的错误是：

The error I am getting is:

LINQ到实体无​​法识别方法'System.String get_Item（System.String），它不能转换到存储库的前pression。

LINQ to Entities does not recognize the method 'System.String get_Item (System.String)', which can not be converted into an expression of the repository.

推荐答案

对数据库进行LINQ查询将被转换为SQL它们可以被执行之前;但集[txtDtInicial] 不能转换为SQL，因为没有相应的SQL语法，反正数据库不能访问到集。你需要提取集[txtDtInicial] 给一个变量第一，并在查询中只使用这个变量。

Linq queries performed against a database are translated to SQL before they can be executed; but collection["txtDtInicial"] can't be translated to SQL, because there is no equivalent SQL syntax, and anyway the database doesn't have access to collection. You need to extract collection["txtDtInicial"] to a variable first, and use only this variable in the query.

下面是我会做：

DateTime dtInicio = DateTime.MinValue;
DateTime dtFim = DateTime.MaxValue;
Int32 codStatus = 0;

if(!string.IsNullOrEmpty(collection["txtDtInicial"]))
    dtInicio = Convert.ToDateTime(collection["txtDtInicial"]);
if(!string.IsNullOrEmpty(collection["txtDtFinal"]))
    dtFim = Convert.ToDateTime(collection["txtDtFinal"]);
if (!string.IsNullOrEmpty(collection["StatusCliente"]))
    codStatus = Convert.ToInt32(collection["StatusCliente"]);

var listCLientResult = (from c in db.tbClientes
                       orderby c.id
                        where (c.effdt >= dtInicio) &&
                             (c.effdt <= dtFim) &&
                             (c.cod_status_viagem == codStatus)
                             select c);
return View(listCLientResult);

通过初始化 dtInicio 和 dtFim 来MINVALUE和MaxValue的，你并不需要检查它们是否被定义在查询中。

By initializing dtInicio and dtFim to MinValue and MaxValue, you don't need to check whether they are defined in the query.

这篇关于LINQ到实体无​​法识别方法'System.String get_Item（System.String）“，的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！