C#-Error 26- Locating Server/Instance Specified

Question

I am attempting to run a program that gets data from a remote SQL Server, but when I run the program the debugger says "Error Locating Server/Instance Specified"

I searched the web and Stack Overflow and tried many things, but nothing worked!

What am I doing wrong here?

private void txtsearch_Click(object sender, EventArgs e)
    {
        SqlConnection conn = new SqlConnection("Server=.\\MSSQLSERVER;AttachDbFilename = C:\\Program Files\\Microsoft SQL Server\\MSSQL11.MSSQLSERVER\\MSSQL\\DATA\\Education.mdf; Database= education;Trusted_Connection=Yes;");
        DataTable dt = new DataTable();
        SqlDataAdapter SDA = new SqlDataAdapter("Select * From Education Where NationalKey "+ txtNationalKey.Text, conn);
        SDA.Fill(dt);
        dataGridView1.DataSource = dt;

    }

I tried MSSQL11,SQL Express and many other format of string. I opened UDP port 1434,TCP port 1433 and 7200 too.

Answer 1

.\\\\ in your connection string refer to local machine. Set Ip or machine name of the SqlServer machine.