为什么即使列名可用也出现无效列名的错误 [英] why i m getting error of invalid column name even when column name is available

问题描述

string checkl = "SELECT COUNT(*) FROM Counter WHERE leftcount=1";
                com = new SqlCommand(checkl, con);
                com.CommandType = CommandType.Text;
                da = new SqlDataAdapter(com);
                DataTable dtcheckl = new DataTable();
                da.Fill(dtcheckl);

                int lcount = 0;
                lcount =Convert.ToInt32(dtcheckl.Rows[0]["leftcount"].ToString());//ERROR

我收到无效的列名错误，但是当我在数据库中运行相同的查询时，我得到了输出，但是在前端，我得到错误了，为什么?

i am getting invalid column name error but when i run same query in database i get the output but here in front end i m getting error why?

推荐答案

，因为您要引用.NET中未在SQL中检索的列.
从计数器WHERE leftcount = 1中选择COUNT(*).您正在选择COUNT(*)\
您应该选择在代码中使用的leftcount.

Because you are referring column in .NET that is not retrived in SQL.
SELECT COUNT(*) FROM Counter WHERE leftcount=1. You are selecting COUNT(*)\
you should be selecting leftcount for using it in Code .

在select语句中，您得到的是计数而不是列数据.您可以将查询设置为

In the select statement you are getting the count not the column data . you can set the query as

SELECT COUNT (*) as  leftcount FROM Counter WHERE leftcount=1

希望您在修改查询后能得到理想的结果.

Hope you''ll get the desired result after modifying your query.

编写如下代码.

Write your code as below.

string checkl = "SELECT COUNT(*) as CountValue FROM Counter WHERE leftcount=1";
com = new SqlCommand(checkl, con);
com.CommandType = CommandType.Text;
da = new SqlDataAdapter(com);
DataTable dtcheckl = new DataTable();
da.Fill(dtcheckl);
 
int lcount = 0;
lcount =Convert.ToInt32(dtcheckl.Rows[0]["CountValue"].ToString());

这应该可行.

This should work.

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