当我附加mdf文件时，在与sql server建立连接时发生网络相关错误或实例特定错误

我写了一个c# Windows应用程序来存储一些数据到SQL server数据库，但是当我尝试将我的MDF数据库文件附加到visual studio时，上面的错误出现在下面的代码中，我能做什么?谢谢。

public partial class Add_Client : Form
{
    SqlConnection clientConnection;
    string connString;
    SqlCommand insertCommand; 

 public Add_Client()
    {
        InitializeComponent();
        connString = "Data Source=ESLAM''MSSQLSERVER;Initial Catalog=Clients; Integrated security=true ";
        clientConnection = new SqlConnection();
        clientConnection.ConnectionString = connString;
    }

    private void button1_Click(object sender, EventArgs e)
    {
         try
        {
            SqlCommand insertCommand = new SqlCommand();
            insertCommand.Connection = clientConnection;
            insertCommand.CommandText = "INSERT INTO Client_Info values(@Client_Name,@Autorization_No,@Issue_Type,@Status)";
            insertCommand.Parameters.Add("@Client_Name", SqlDbType.NVarChar, 60).Value = txt_Name.Text;
            insertCommand.Parameters.Add("@Autorization_No", SqlDbType.Int, 60).Value = txt_Auth.Text.ToString();
            insertCommand.Parameters.Add("@Issue_Type", SqlDbType.Text, 200).Value = txt_Iss.Text;
            insertCommand.Parameters.Add("@Status", SqlDbType.Text, 200).Value = txt_Iss.Text;
            //insertCommand.Parameters.Add("@Date To Memorize", SqlDbType.Date, 15).Value=Ca_Mem.se;
            insertCommand.Connection.Open();
            insertCommand.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            if (clientConnection != null)
            {
                clientConnection.Close();
            }
        }
        }
}