Replace DBNull with null

Question

I´m currently working on a C# WPF project that uses a MS SQL-Server.

Since working with DBNull values is somewhat annoying, I wondered if it´s possible to somehow convert those into regular c# null values.

I wrote a little wrapper to connect to the database, execute an SELECT statement and return the result as a DataTable :

public static DataTable getResultTable(string select, params DbParameter[] parameters) {
    using (OleDbConnection connection = new OleDbConnection(_connectionString)) {
        connection.Open();
        try {
            using (OleDbCommand cmd = new OleDbCommand(select, connection)) {
                for (int i = 0; i < parameters.Length; i++) {
                    cmd.Parameters.Add("?", parameters[i].type).Value = parameters[i].value;
                }
                using (OleDbDataAdapter adapter = new OleDbDataAdapter(cmd)) {
                    using (DataTable dt = new DataTable()) {
                        adapter.Fill(dt);

                        //Here my DataTable dt is filled with the required data
                        //I´d like to replace all DBNull Values with regular null values now

                        return dt;
                    }
                }
            }
        } finally {
            connection.Close();
        }
    }
}

I sure could loop over every single field of the DataTable and replace the value in case it´s DBNull, but I wonder if there is a better way.

EDIT:

For anyone stumbling across this question. Using the answer of @Sergiu Muresan I created two Extension Methods, that exactly fit my needs:

public static class ExtensionMethods {
    public static T? GetValue<T>(this DataRow row, string columnName) where T : struct {
        if (row[columnName] is T)
            return (T)row[columnName];
        return null;
    }

    public static T GetValue<T>(this DataRow row, string columnName, T defaultValue) {
        return (row[columnName] is T) ? (T)row[columnName] : defaultValue;
    }
}

• The first Methods restricts The T-Patameter to struct only, which means you can only use value-types (int, bool, double, ...) here, but no object-types (string, customObjects, ...).

  It will then return the Nullable version of given type (e.g. int? for int), which will be null if the value was DBNull.

• The second method can be used for both value-types and object-types. Here you also have to give a default value, which will be returned
  when the vlaue is DBNull. This method can also be used to change DBNull to null, but for object-types only, since those always can be set to null and don´t need a specail Nullable.

Answer 1

Extension methods enable you to add methods to existing types without creating a new derived type, recompiling, or otherwise modifying the original type. An extension method is a special kind of static method, but they are called as if they were instance methods on the extended type.

public static class ExtensionMethods
{
    public static T GetValue<T>(this DataRow row, string columnName, T defaultValue = default(T))
    {
        var obj = row[columnName];

        // if obj is DbNull it will skip this and return the default value
        if (obj is T)
        {
            return (T)obj;
        }

        return defaultValue;
    }
}

And you can use it like this

var dt = getResultTable(...);

var value1 = dt.Rows[0].GetValue<int>("ColumnName");

var value2 = dt.Rows[0].GetValue<int>("ColumnName", 10); // you can also specify a different default value if needed