Added database connection check at application startup

BealeEngineering/BealeEngineering.Accounts/frmMain.cs

@@ -26,6 +26,15 @@ namespace BealeEngineering.Accounts
         {
             InitializeComponent();
             sqlConnectionString = ConfigurationManager.ConnectionStrings["BealeEngSQLDb"].ToString();
+
+            // test for sql connection
+            string dbConnMessage = new Core.Data.Database.Connection(sqlConnectionString).IsServerConnected();
+            if (dbConnMessage != null)
+            {
+                MessageBox.Show(dbConnMessage, "Database connection error", MessageBoxButtons.OK);
+                Environment.Exit(0);
+            }
+
             assignInvoice = new Core.Logic.Sale.AssignInvoice(sqlConnectionString);
             UpdateInvoiceImportText();
         }

BealeEngineering/BealeEngineering.Core/Data/Database/Connection.cs

@@ -22,5 +22,21 @@ namespace BealeEngineering.Core.Data.Database
 
             this.sqlConnectionString = sqlConnectionString;
         }
+
+        public string IsServerConnected()
+        {
+            using (SqlConnection conn = new SqlConnection(sqlConnectionString))
+            {
+                try
+                {
+                    conn.Open();
+                    return null;
+                }
+                catch (SqlException ex)
+                {
+                    return ex.InnerException;
+                }
+            }
+        }
     }
 }