error to connect sql

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ASP.NET

SQL

hi how can i solve this error in connect to sql to create a database or add data to database:
i install sqlexpress with dotnet

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)

!!!!!!!!my sql server is good work
because when i and drag a sqldatasource to my page and related a datagrid with it
my database work good

i used this code for create db

{
  string strsql, strcon;
        strcon = "Data Source=(1-pc);Initial Catalog=neww.mdf;Integrated Security=true";
        SqlConnection con = new SqlConnection(strcon);
        SqlCommand cmdclasf;
        strsql = "create database product";
        con.Open();
        cmdclasf = new SqlCommand(strsql, con);
        int count = cmdclasf.ExecuteNonQuery();
        con.Close();
        if (count == 0)
            Label1.Text = "not create";
        else
            Label1.Text = "created";
}