Insert data to a SQL database in .NET Core 3.1 using C# receives an error

Question

I have created a SQL DataBase (DatabaseTest.mdf) in Visual Studio 2019 Preview (.NET Core 3.1, Windows Form Application). It is my first time, I am trying to do this. I run the database locally on my computer.

The database consists of 4 columns:

• First Name
  
• Last Name
  
• PhoneNumber
  
• Salary
  

Now, I am trying to use C# to programatically ADD a row with information to this database.

The code is the below:

    using System.Data.SqlClient;

    private void button1_Click(object sender, EventArgs e)
    {
        string connectionString = GetConnectionString();

        SqlConnection con = new SqlConnection(connectionString); 
        SqlCommand cmd = new SqlCommand("sp_insert", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.AddWithValue("@First Name", "Peter");
        cmd.Parameters.AddWithValue("@Last Name", "Smith");
        cmd.Parameters.AddWithValue("@PhoneNumber", "5548945667");
        cmd.Parameters.AddWithValue("@Salary", 50000);
        con.Open();
        int i = cmd.ExecuteNonQuery();

        con.Close();

        if (i != 0)
        {
            MessageBox.Show(i + "Data Saved");
        }
    }
    static private string GetConnectionString()
    {
        return "Data Source=(LocalDB)/MSSQLLocalDB;AttachDbFilename=C:/Users/andre/source/repos/TestDatabaseCreation/DatabaseTest.mdf;Integrated Security=True";
    }

However, when I now run this code by clicking on the button. I receive this error:
System.Data.SqlClient.SqlException: '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)'

Win32Exception: Network path not found.

I have copied this connection string from the DatabaseTest.mdf properties exactly. So the path to the DatabaseTest.mdf below is correct etc
"Data Source=(LocalDB)/MSSQLLocalDB;AttachDbFilename=C:/Users/andre/source/repos/TestDatabaseCreation/DatabaseTest.mdf;Integrated Security=True"

I wonder what the problem is that I get this error message?

(I attach a screenshot on the link below also from Visual Studio 2019 Preview .NET Core 3.1)
Image of the error in C# code behind in Visual Studio 2019 Preview

Answer 1

First, you can ensure SQL Server Express is installed and working by the following steps

1. Open Visual Studio Installer >> Modify

Expand .Net desktop development

Scroll down and check SQL Server Express is installed or not

[

if it is installed go to step 2

2. Open Server Explorer

Connect to Database

Choose Data Source >> Microsoft SQL Server Database File

Add Connection >> Browse to your database file, and make sure to Test Connection, then OK

After that, inside Server Explorer will display the connections, right click on that >> properties

Then you can get the Connection String

Second, with Connection String got above, you can check it work or not by

SqlConnection cnn = new SqlConnection(**connectionString**);

cnn.Open();

// not do anything yet

cnn.Close();

Then run to make sure you can open the connection to the database

UPDATE :

Check which Stored Procedures you want is existed or not?