Connecting to SQL Server with Visual Studio in C#

Question

namespace FormUI
{
        public partial class Dashboard : Form
        {
            List<Person> people = new List<Person>();

            public Dashboard()
            {
                InitializeComponent();
                listBox1.DataSource = people;
                listBox1.DisplayMember = "FullInfo";
            }

            private void button1_Click(object sender, EventArgs e)
            {
               // Dashboard d = new Dashboard();
                DataAccess db = new DataAccess();
                people=db.GetPeople(textBox1.Text);
            }
        }
}

namespace FormUI
{
    class DataAccess
    {
        public List<Person> GetPeople(string name)
        {
            using (IDbConnection connection = new System.Data.SqlClient.SqlConnection(Helper.CnnVal("databaseEx")))
            {
                var output = connection.Query<Person>($"select * from member").ToList();
                return output;
            }
        }
    }
}

namespace FormUI
{
    public static class Helper
    {
        public static string CnnVal(string na)
        {
            return ConfigurationManager.ConnectionStrings[na].ConnectionString;
        }
    }
}

Config:

<add name="SampleDB" 
     connectionString="Server=local;Database=databaseEx;Trusted_Connection=True;" 
     providerName="System.Data.SqlClient"/>

When I am running this code, I get an error:

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

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

Could you post the connection string section of your config class? — DB101, Jun 19 '18 at 14:23
`ConnectionStrings[na]` is returning `null`. It's probably misplaced on the config XML. — EzLo, Jun 19 '18 at 14:25
Can you check that the enclosing tabs are formed correctly as below. — DB101, Jun 19 '18 at 14:29
SampleDB is the name of the key. So you should use something to the effect of ConfigurationManager.ConnectionStrings["SampleDB"].ConnectionString so call Helper.CnnVal("SampleDB") — L0uis, Jun 19 '18 at 14:29

score 0 · Accepted Answer · answered Jun 19 '18 at 14:41

0

Replace this line in your code

using (IDbConnection connection = new System.Data.SqlClient.SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["SampleDB"].ConnectionString))

answered Jun 19 '18 at 14:41

Mihir Dave

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That worked but agian its giving me a different error instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)' – Manjinder Grewal Jun 19 '18 at 15:03
@ManjinderGrewal you will find this helpful https://stackoverflow.com/questions/18060667/why-am-i-getting-cannot-connect-to-server-a-network-related-or-instance-speci – Mihir Dave Jun 19 '18 at 15:07

Connecting to SQL Server with Visual Studio in C#

1 Answers1