Am getting error while connecting by db with visual studio 2019

Bhavesh R

5y3.8k.NET

using System;

using System.Collections.Generic;

using System.Configuration;

using System.Data.SqlClient;

using System.Linq;

using System.Web;

namespace aspsnippets.Models

{

public class DBconnection

{

public List DBconnect()

{

List chartData = new List();

string connectionString = ConfigurationManager.ConnectionStrings["conmydb"].ToString();

SqlConnection sqlConnection = new SqlConnection(connectionString);

string cmd1 = "select * from piechart";

SqlCommand sqlCommand = new SqlCommand(cmd1, sqlConnection);

SqlDataReader sqlDataReader = sqlCommand.ExecuteReader();

while(sqlDataReader.Read())

{

chartData.Add(new asppiechart

{

Month = sqlDataReader["Month"].ToString(),

Values = sqlDataReader["Values"].ToString()

});

}

return chartData;

}

AM GETTING THIS ERROR:

System.NullReferenceException: 'Object reference not set to an instance of an object.'

System.Configuration.ConnectionStringSettingsCollection.this[string].get returned null.

11 Replies

Know the answer? Post it — somebody with the same question will find it here.

Salman Beg5y ago
In the web.config file you can check the connectionstring. Is all your issue resolved?
Jignesh Kumar5y ago
Web.config file you need to check. Find with conmydb or your database name or DataSource name in config.
Bhavesh R5y ago
yeah am able connect sir.One of my frnd told that to check whether my connection string is declared twice..How to check that??
Jignesh Kumar5y ago
are you able to connect to SQL when you open sql server and check your server name ?

if you are able to connect with server Name "RAMKI\BHAVESH" then your connection string is correct.
Sachin Singh5y ago
copy the proper connection string from the visual studio server explorer, don't write it on your own when you are not sure.
Bhavesh R5y ago
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Web;
namespace aspsnippets.Models
{
public class DBconnection
{
public List DBconnect()
{
List chartData = new List();
string connectionString = ConfigurationManager.ConnectionStrings["conmydb"].ConnectionString;
using (SqlConnection sqlConnection = new SqlConnection(connectionString))
{
SqlCommand sqlCommand = new SqlCommand("SELECT * FROM piechart", sqlConnection);
sqlCommand.CommandType = CommandType.Text;
sqlConnection.Open();
SqlDataReader sqlDataReader = sqlCommand.ExecuteReader();
while (sqlDataReader.Read())
{
chartData.Add(new asppiechart
{
Month = sqlDataReader["Month"].ToString(),
Values = sqlDataReader["Values"].ToString()
});
}
return chartData;
}
}
}
}

Am getting the same error sir!!!

System.NullReferenceException: 'Object reference not set to an instance of an object.'
System.Configuration.ConnectionStringSettingsCollection.this[string].get returned null.

I need to know whether my connecting strng is correct?
Sachin Singh5y ago
copy paste below code and run
public List DBconnect()
{
List chartData = new List();
string connectionString = ConfigurationManager.ConnectionStrings["conmydb"].ConnectionString;
SqlConnection sqlConnection = new SqlConnection(connectionString);
string cmd1 = "select * from piechart";
SqlCommand sqlCommand = new SqlCommand(cmd1, sqlConnection);
sqlConnection.Open();
SqlDataReader sqlDataReader = sqlCommand.ExecuteReader();
while(sqlDataReader.Read())
{
chartData.Add(new asppiechart
{
Month = sqlDataReader["Month"].ToString(),
Values = sqlDataReader["Values"].ToString()
});
}
return chartData;
}
}
Jignesh Kumar5y ago
Can you share code and error you are getting after change done ?
Bhavesh R5y ago
Bhavesh R5y ago
still getting same error
Jignesh Kumar5y ago
Hi,

your are doing minor mistake here please change,
string connectionString = ConfigurationManager.ConnectionStrings["conmydb"].ConnectionString;