Commandbehavior.sequentialaccess异常。尝试从列序号'0'读取无效。

问题描述

我正在使用

EntityDataReader

来填充

List<SelectListItem> products

只有一列类型为string：[prod_name_pharma_form]

我收到此异常：

from MS SQL table that has only one column of type "string": [prod_name_pharma_form]
I am getting this exception:

Attempt to read from column ordinal '0' is not valid.  With CommandBehavior.SequentialAccess, you may only read from column ordinal '1' or greater.'

我尝试过：



我使用的代码与多列的表格完美配合：

What I have tried:

I am using this code that works perfectly with tables of more than one column:

<pre>public JsonResult AjaxProducts()
        {
            List<SelectListItem> products = new List<SelectListItem>();
            string query = "SELECT p.prod_name_pharma_form FROM Entities.FDF_FAMILY_PROD_NAME as p";
            using (EntityConnection con = new EntityConnection("name=Entities"))
            {
                using (EntityCommand cmd = new EntityCommand(query))
                {
                    cmd.CommandType = CommandType.Text;
                    cmd.Connection = con;
                    con.Open();
                    using (EntityDataReader sdr = cmd.ExecuteReader(System.Data.CommandBehavior.SequentialAccess))
                    {
                        while (sdr.Read())
                        {
                            products.Add(new SelectListItem
                            {
                                Value = sdr["prod_name_pharma_form"].ToString(),
                                Text = sdr["prod_name_pharma_form"].ToString()
                            });
                        }
                    }
                }
            }

            return Json(products);
        }

我理解使用SequentialAccess我必须以正确的顺序读取（选择）列以避免这种异常，但是我该怎么做如果有一个列的表？

I understand that with "SequentialAccess" I have to read (select) columns in the correct order to avoid this kind of exceptions, but What do I do in case having a table of one column?

推荐答案

while (sdr.Read())
{
    string name = sdr["prod_name_pharma_form"].ToString();

    products.Add(new SelectListItem
    {
        Value = name,
        Text = name
    });
}

这篇关于Commandbehavior.sequentialaccess异常。尝试从列序号'0'读取无效。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！