App.Config file connection string but its connected and am getting the null value reference error

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Hi All,

Am new in WPF application. I tried connect asp.net with sql server 2008 database. I am using App.Config connection string but its connected and am getting the null value reference error. I know this error why this came in my app the database connectionstring problem. Here, I below added the my connection string in App.Config file. Can anyone please help.

Config File Code:-

XML

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionstrings>
    <add ConnectionString="Data Source=xxxxxx;Initial Catalog=WPFTraining;Persist Security Info=True;User ID=xxxxxx;Password=xxxxxx;Pooling=False" providerName="System.Data.SqlClient" name="ConString"/>
  </connectionstrings>
</configuration>

Code Behind:-

C#

private void FillDataGrid()
        {
            string ConString = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
            string CmdString = string.Empty;
            using (SqlConnection con = new SqlConnection(ConString))
            {
                CmdString = "SELECT emp_id, name, dept, salary FROM employee";
                SqlCommand cmd = new SqlCommand(CmdString, con);
                SqlDataAdapter sda = new SqlDataAdapter(cmd);
                DataTable dt = new DataTable("employee");
                sda.Fill(dt);
                grdemployee.ItemsSource = dt.DefaultView;
            }
        }

Posted 12-Nov-13 22:54pm

IsaiSelvan

Updated 13-Nov-13 0:30am

Sampath Lokuge

v3

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Comments

thatraja 13-Nov-13 5:03am

Include the code in your question

IsaiSelvan 13-Nov-13 5:10am

this is my code behind code:

private void FillDataGrid()
{
string ConString = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
string CmdString = string.Empty;
using (SqlConnection con = new SqlConnection(ConString))
{
CmdString = "SELECT emp_id, name, dept, salary FROM employee";
SqlCommand cmd = new SqlCommand(CmdString, con);
SqlDataAdapter sda = new SqlDataAdapter(cmd);
DataTable dt = new DataTable("employee");
sda.Fill(dt);
grdemployee.ItemsSource = dt.DefaultView;
}
}

thatraja 13-Nov-13 5:37am

In which line the error occurs?

Jamie Head 10-Aug-20 16:19pm

I am getting the same error here -> https://www.codeproject.com/Questions/5276170/Sqlite-Csharp-why-am-I-getting-a-null-connection I dont seem to know what is causing it. Maybe its something to do with it being a console app. I have tried manually giving it a connectionString and I still get the same error.

3 solutions

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deepgalley · Answer 1 · 2013-11-13T01:14:00

Solution 1

You need to open the connection
before
SqlCommand cmd = new SqlCommand(CmdString, con);
Put
con.Open();

then try it

Posted 13-Nov-13 1:14am

deepgalley

Comments

IsaiSelvan 13-Nov-13 7:39am

I am getting same error message deepgalley

[no name] 13-Nov-13 8:25am

just debug the code and let me know on exactly which line getting error.

King Fisher · Answer 2 · 2013-11-18T22:41:00

XML

<configuration>
  <connectionstrings>
    <<big>add name="ConString"</big> ConnectionString="Data Source=xxxxxx;Initial Catalog=WPFTraining;Persist Security Info=True; providerName="System.Data.SqlClient" name="ConString"/>
  </connectionstrings>
</configuration>

for windows authentication

XML

<configuration>
  <connectionstrings>
    <add ConnectionString="Data Source=xxxxxx;Initial Catalog=WPFTraining;User ID=xxxxxx;Password=xxxxxx/>
  </connectionstrings>
</configuration>

for sql server authentication

..try this

deepgalley · Answer 3 · 2013-11-18T20:34:00

Solution 2

Try to give the connection directly.

Posted 18-Nov-13 20:34pm