Update SqlDataReaderExtensions.cs

In #dde0ade, we replaced `reader.GetValue()` with strongly typed extension methods, such as `reader.GetInteger()`. Under the hood, these simply looked up the ordinal value of the column name, and then called the underlying `SqlDataReader` methods such as `GetInt32()`, `GetBoolean()`, &c. Unfortunately, that approach doesn't work because the values being returned aren't actually e.g. `INT`, `BIT`, &c. Instead, they're (almost always) strings, especially when they map to `AttributeKey` or `AttributeValue` (as is true of attributes, including `Key`, `ParentId`, `ContentType`, `IsHidden`, &c.). As such, instead of calling the underlying strongly typed methods, we need to call `SqlDataReader.GetValue()` and then do a conversion. To support this, the private `GetValue()` extension is now setup to instead accept a `TryParse` delegate so that e.g. `Boolean.TryParse` can be passed as the delegate. This isn't all that elegant, but it should work, and it still results in much cleaner code in `SqlTopicRepository`, which was the original objective.

Author: JeremyCaney

OnTopic.Data.Sql/SqlDataReaderExtensions.cs

@@ -19,6 +19,12 @@ namespace OnTopic.Data.Sql {
   /// </summary>
   internal static class SqlDataReaderExtensions {
 
+
+    /*==========================================================================================================================
+    | DELEGATE: TRY PARSE
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    public delegate bool TryParse<in String, U, out Boolean>(String input, out U output);
+
     /*==========================================================================================================================
     | METHOD: GET INTEGER
     \-------------------------------------------------------------------------------------------------------------------------*/
@@ -28,7 +34,7 @@ internal static class SqlDataReaderExtensions {
     /// <param name="reader">The <see cref="SqlDataReader"/> object.</param>
     /// <param name="columnName">The name of the column to retrieve the value from.</param>
     internal static int GetInteger(this SqlDataReader reader, string columnName) =>
-      GetValue<int>(reader, columnName, reader.GetInt32, -1);
+      GetValue<int>(reader, columnName, Int32.TryParse, -1);
 
     /*==========================================================================================================================
     | METHOD: GET STRING
@@ -39,7 +45,7 @@ internal static int GetInteger(this SqlDataReader reader, string columnName) =>
     /// <param name="reader">The <see cref="SqlDataReader"/> object.</param>
     /// <param name="columnName">The name of the column to retrieve the value from.</param>
     internal static string GetString(this SqlDataReader reader, string columnName) =>
-      GetValue<string>(reader, columnName, reader.GetString, String.Empty);
+      GetValue<string>(reader, columnName, (string source, out string value) => { value = source; return true; }, String.Empty);
 
     /*==========================================================================================================================
     | METHOD: GET DATE/TIME
@@ -50,7 +56,7 @@ internal static string GetString(this SqlDataReader reader, string columnName) =
     /// <param name="reader">The <see cref="SqlDataReader"/> object.</param>
     /// <param name="columnName">The name of the column to retrieve the value from.</param>
     internal static DateTime GetDateTime(this SqlDataReader reader, string columnName) =>
-      GetValue<DateTime>(reader, columnName, reader.GetDateTime, DateTime.MinValue);
+      GetValue<DateTime>(reader, columnName, DateTime.TryParse, DateTime.MinValue);
 
     /*==========================================================================================================================
     | METHOD: GET BOOLEAN
@@ -61,7 +67,7 @@ internal static DateTime GetDateTime(this SqlDataReader reader, string columnNam
     /// <param name="reader">The <see cref="SqlDataReader"/> object.</param>
     /// <param name="columnName">The name of the column to retrieve the value from.</param>
     internal static bool GetBoolean(this SqlDataReader reader, string columnName) =>
-      GetValue<bool>(reader, columnName, reader.GetBoolean, false);
+      GetValue<bool>(reader, columnName, Boolean.TryParse, false);
 
     /*==========================================================================================================================
     | METHOD: GET VALUE
@@ -71,18 +77,22 @@ internal static bool GetBoolean(this SqlDataReader reader, string columnName) =>
     /// </summary>
     /// <param name="reader">The <see cref="SqlDataReader"/> object.</param>
     /// <param name="columnName">The name of the column to retrieve the value from.</param>
-    /// <param name="getter">Function to call in order to retrieve the strongly typed value from the reader.</param>
+    /// <param name="parser">Function to call in order to convert the string value to a strongly typed value.</param>
     /// <param name="defaultValue">The default value, in case <see cref="DBNull"/> is returned.</param>
     private static T GetValue<T>(
       SqlDataReader reader,
       string columnName,
-      Func<int, T> getter,
+      TryParse<string, T, bool> parser,
       object defaultValue
     ) {
       Contract.Requires(columnName, nameof(columnName));
       var ordinal = reader.GetOrdinal(columnName);
-      if (!reader.IsDBNull(ordinal)) {
-        return getter(ordinal);
+      if (reader.IsDBNull(ordinal)) {
+        return (T)defaultValue;
+      }
+      var value = reader.GetValue(ordinal).ToString();
+      if (parser(value, out var output)) {
+        return output;
       }
       return (T)defaultValue;
     }