How do I resolve this issue ?

See more:

ASP.NET

SQL

No errors and warnings but i am not getting the output.

showing:

Exception thrown: 'System.Data.SqlClient.SqlException' in System.Data.dll
An exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll but was not handled in user code
A network-related or 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)

'iisexpress.exe' (CLR v4.0.30319: /LM/W3SVC/2/ROOT-1-131831092354667571): Loaded 'C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\Common7\IDE\PrivateAssemblies\Runtime\Microsoft.VisualStudio.Debugger.Runtime.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
The program '[14544] iisexpress.exe' has exited with code -1 (0xffffffff).

What I have tried:

namespace Emp
{
public partial class DBfetch : System.Web.UI.Page
{
public static int i;
SqlConnection conn=null;
SqlDataAdapter da;
DataTable dt = new DataTable();
DataRow dr;
protected void Page_Load(object sender, EventArgs e)
{
string connectionstring = "Data Source=DESKTOP-KR73POJ;Initial Catalog=Test; Persist Security Info=True;User ID=sa;Password=admin";
conn = new SqlConnection(connectionstring);
conn.Open();
da = new SqlDataAdapter("select * from testtable", conn);
da.Fill(dt);
conn.Close();
}
protected void Button1_Click(object sender, EventArgs e)
{
i = 0;
dr = dt.Rows[i];
TextBox1.Text = Convert.ToString(dr[0]);
TextBox2.Text = Convert.ToString(dr[1]);
TextBox3.Text = Convert.ToString(dr[2]);
}
protected void Button2_Click(object sender, EventArgs e)
{
if (i == 0)
Response.Write("First record !");
else
i--;
dr = dt.Rows[i];
TextBox1.Text = Convert.ToString(dr[0]);
TextBox2.Text = Convert.ToString(dr[1]);
TextBox3.Text = Convert.ToString(dr[2]);
}
protected void Button3_Click(object sender, EventArgs e)
{
if (i == (dt.Rows.Count - 1))
Response.Write("Last record !");
else
i++;
dr = dt.Rows[i];
TextBox1.Text = Convert.ToString(dr[0]);
TextBox2.Text = Convert.ToString(dr[1]);
TextBox3.Text = Convert.ToString(dr[2]);
}

}

}