# Manage exceptions when selecting, modifying data

The `SqlException` has a **Number** property that you can check.

```csharp
catch (SqlException e)
{
   switch (e.Number)
   {
      case 2601: // duplicate error
         // Do something.
         break;
      default:
         throw;
   }
 }
```

The following table describes the possible values for this property:

| Source of Error                                                      | SqlError.Number                                                                                                        | SqlException has inner Win32Exception (beginning with.NET Framework 4.5) |
| -------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------ |
| Error from server                                                    | <p>Server error code<br><br> This number corresponds to an entry in the <code>master.dbo.sysmessages</code> table.</p> | No                                                                       |
| Connection timeout                                                   | -2                                                                                                                     | Yes (Number = 258)                                                       |
| Communication error (non-LocalDB)                                    | Win32 error code                                                                                                       | Yes (Number = Win32 error code)                                          |
| Communication error (LocalDB)                                        | Win32 error code                                                                                                       | No                                                                       |
| Encryption capability mismatch                                       | 20                                                                                                                     | No                                                                       |
| Failed to start LocalDB                                              | Win32 error code                                                                                                       | No                                                                       |
| Read-only routing failure / Server had severe error processing query | 0                                                                                                                      | No                                                                       |