Error Handling When Using Dictionary

Question

I have set up a Dictionary that calls on a class to fill a DataGridView via SQL statements. The problem is in two (out of 5) instances the value passed HAS to be an integer, but the value comes from a textbox so it is being passed as string. Before I set these Dictionaries up I was just using a switch statement that can be seen here. In my switch statement I simply added:

int n;
bool isNumber = int.TryParse(textBox.Text, out n);

if (!isNumber)
{
  MessageBox.Show("Input must be an integer");
  break;
}

to the two cases that needed the value to be an integer type.

Any idea on how I can add error handling to this? Preferably a message box that just says "value needs to be an integer".

    private void findScriptsQueryButton_Click(object sender, EventArgs e)
    {
        SqlConnection connection = new SqlConnection();
        string value = this.valueTextBox.Text;
        connection.ConnectionString = GetSqlConnection[serverComboBox.SelectedItem.ToString()];
        findScriptsDataGrid.DataSource = GetDataSource[findByComboBox.SelectedItem.ToString()](connection, value).Tables[0];
    }
    private static TableAdapters.FindScript dataSource = new TableAdapters.FindScript();
    private static readonly Dictionary<String, Func<SqlConnection, String, DataSet>> GetDataSource = new Dictionary<String, Func<SqlConnection, String, DataSet>>()
    {
        {"Target VDN", dataSource.FillByTargetVDN},
        {"Skill Group", dataSource.FillBySkillGroup},
        {"Translation Route Pool", dataSource.FillByTranslationRoutePool},
        {"Name", dataSource.FillByName},
        {"Label", dataSource.FillByLabel}
    };

    private static readonly Dictionary<String, String> GetSqlConnection = new Dictionary<String, String>()
    {
        {"SERVER01", ConfigurationManager.ConnectionStrings["csS01"].ConnectionString},
        {"SERVER02", ConfigurationManager.ConnectionStrings["csS02"].ConnectionString}
    };

Answer 1

In your data structure include a validator (this should probably be a Predicate<String>); most of the predicates will just return true, but the two that require integers will have a nontrivial validator that checks for integer.

So I guess the type should be Dictionary<String, Tuple<Func<SqlConnection, String, DataSet>>,Predicate<String>>

Answer 2

I haven't tested, so cannot verify about errors but you could try something like this -

1. Create validator functions for validating input -

   public bool DummyValidator(string input)
   {
   
       return true;
   }
   
   public bool ValidateIntegerInput(string input)
   {
       int n;
       bool isNumber = int.TryParse(input, out n);
   
       if (!isNumber)
       {
           MessageBox.Show("Input must be an integer");\
           return false;
       }
       return true;
   }
   

2. Create dictionary to hold them -

   private static readonly Dictionary<String, Func<String, Boolean>> GetValidator = new Dictionary<String, Func<String, Boolean>>()
   {
       {"Target VDN", dataSource.ValidateIntegerInput},
       {"Skill Group", dataSource.ValidateIntegerInput},
       {"Translation Route Pool", dataSource.DummyValidator},
       {"Name", dataSource.DummyValidator},
       {"Label", dataSource.DummyValidator}
   };
   

3. Then validate before calling methods -

   SqlConnection connection = GetSqlConnection();
   string value = this.ValueTextBox.Text;
   
   if (GetValidator[this.FindByComboBox.SelectedItem.ToString()](textBox.Text)){
   
       this.FindScriptsDataGrid.DataSource = switchReplacement[this.FindByComboBox.SelectedItem.ToString()](connection, value).Tables[0];
   
   }
   

You can map other validators accordingly.