Check all values of specific column to define the datatype in DGV

Question

I'm asking your help to know if exists a fast method to check if all the values in a specific column of a DataTable/Datagridview are DateTime or numbers.

I'm trying to make a generic method to put specific formats in any column in a DGV.

I have information from TEXT files / Excel or XML files without previously data type definition

Thanks!

Answer 1

You can bury the loop in an extension method. The end result will need a loop somewhere, though, even if the loop is hidden inside Linq operations. For example, you could write this extension method:

public static void ApplyColumnFormatting(this System.Data.DataTable table, string column, Action formatDateTime, Action formatNumeric)
{
    bool foundNonDateTime = false;
    bool foundNonNumeric = false;

    DateTime dt;
    Double num;

    foreach (System.Data.DataRow row in table.Rows)
    {
        string val = row[column] as string;

        // Optionally skip this iteration if the value is not a string, depending on your needs.
        if (val == null)
            continue;

        // Check for non-DateTime, but only if we haven't already ruled it out
        if (!foundNonDateTime && !DateTime.TryParse(val, out dt))
            foundNonDateTime = true;

        // Check for non-Numeric, but only if we haven't already ruled it out
        if (!foundNonNumeric && !Double.TryParse(val, out num))
            foundNonNumeric = true;

        // Leave loop if we've already ruled out both types
        if (foundNonDateTime && foundNonNumeric)
            break;
    }

    if (!foundNonDateTime)
        formatDateTime();
    else if (!foundNonNumeric)
        formatNumeric();
}

Then you can call it like this:

System.Data.DataTable table = ...;

table.ApplyColumnFormatting("Column_Name",
    () => { /* Apply DateTime formatting here */ },
    () => { /* Apply Numeric formatting here */ }
);

This is fast in the sense that it does not check any more rows than necessary, and it does not continue checking a given type after it has been ruled out.