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}
 };

• JohnP: Clarification on the text box: Does it have to be a text box? Or can you make it a different type of input?
• aaronmallen: In this case the text box will be the most efficient solution. It's used to pass a parameter to a query which can literally be hundreds of thousands of possible strings or integers.
• JohnP: If it can be hundreds of thousands, then how are you restricting it in only 2 of 5 instances?
• aaronmallen: "Target VDN" and "Skill Group" are the only two queries in the dictionary that REQUIRE an integer value.
• radarbob: Take a look at the ErrorProvider class. And the StackOverflow errorprovider tag

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.