Added comments

Added check if given class is invalid
Changed BuildQuery to support recursive object[] copying
Changed structure
Added DbFunction to handle all Db-related stuff

Database-Attribute_System/QueryBuilder.cs

@@ -7,21 +7,29 @@ namespace eu.railduction.netcore.dll.Database_Attribute_System
 {
     public class QueryBuilder
     {
+        /// <summary>
+        /// Builds an SELECT-Sql-query based on an object<para/>
+        /// Object needs to have at least 1 primary-key!
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="classObject">Given object (marked with Db-attributes)</param>
+        /// <returns>SELECT-Sql-query</returns>
         public static string SelectByPrimaryKeys<T>(T classObject)
         {
             Type classType = classObject.GetType();
 
             // Get db-table-name from class
-            string tableName = Function.GetDbTableName(classType);
+            string tableName = DbFunction.GetDbTableName(classType);
 
             // Get class db-fields
             Dictionary<string, object> dbPrimaryKeys = new Dictionary<string, object>() { };
             Dictionary<string, object> dbAttributes = new Dictionary<string, object>() { };
             Dictionary<string, object> dbForeignKeys = new Dictionary<string, object>() { };
-            Function.ReadDbClassFields(classObject, ref dbPrimaryKeys, ref dbAttributes, ref dbForeignKeys);
+            DbFunction.ReadDbClassFields(classObject, ref dbPrimaryKeys, ref dbAttributes, ref dbForeignKeys);
+            if (dbPrimaryKeys.Count == 0) throw new InvalidOperationException($"Cannot generate SQL-Query of '{classType.Name}'. No primary-key/s found!");
 
             // Build where statements with primaryKey/s
-            object[] param = Function.BuildKeyEqualQuery(dbPrimaryKeys, " AND ");
+            object[] param = DbFunction.BuildKeyEqualQuery(dbPrimaryKeys, " AND ");
             // Add SQL-command part
             param[0] = $"SELECT * FROM {tableName} WHERE "+ param[0];
             
@@ -29,33 +37,40 @@ namespace eu.railduction.netcore.dll.Database_Attribute_System
             return BuildQuery(param);
         }
 
-
+        /// <summary>
+        /// Builds an UPDATE-Sql-query based on an object<para/>
+        /// Object needs to have at least 1 primary-key!
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="classObject">Given object (marked with Db-attributes)</param>
+        /// <returns>UPDATE-Sql-query</returns>
         public static string UpdateByPrimaryKeys<T>(T classObject)
         {
             Type classType = classObject.GetType();
 
             // Get db-table-name from class
-            string tableName = Function.GetDbTableName(classType);
+            string tableName = DbFunction.GetDbTableName(classType);
 
             // Get class db-fields
             Dictionary<string, object> dbPrimaryKeys = new Dictionary<string, object>() { };
             Dictionary<string, object> dbAttributes = new Dictionary<string, object>() { };
             Dictionary<string, object> dbForeignKeys = new Dictionary<string, object>() { };
-            Function.ReadDbClassFields(classObject, ref dbPrimaryKeys, ref dbAttributes, ref dbForeignKeys);
+            DbFunction.ReadDbClassFields(classObject, ref dbPrimaryKeys, ref dbAttributes, ref dbForeignKeys);
+            if (dbPrimaryKeys.Count == 0) throw new InvalidOperationException($"Cannot generate SQL-Query of '{classType.Name}'. No primary-key/s found!");
 
             // Add foreign-keys to attributes
-            foreach(KeyValuePair<string, object> dbForeignKey in dbForeignKeys)
+            foreach (KeyValuePair<string, object> dbForeignKey in dbForeignKeys)
             {
                 dbAttributes.Add(dbForeignKey.Key, dbForeignKey.Value);
             }
 
             // Build set-parameters
-            object[] paramSet = Function.BuildKeyEqualQuery(dbAttributes, ", ");
+            object[] paramSet = DbFunction.BuildKeyEqualQuery(dbAttributes, ", ");
             // Add SQL-command part
             paramSet[0] = $"UPDATE {tableName} SET "+ paramSet[0];
 
             // Build where-parameters
-            object[] paramWhere = Function.BuildKeyEqualQuery(dbPrimaryKeys, " AND ");
+            object[] paramWhere = DbFunction.BuildKeyEqualQuery(dbPrimaryKeys, " AND ");
             // Add SQL-command part
             paramWhere[0] = " WHERE "+ paramWhere[0];
 
@@ -63,21 +78,29 @@ namespace eu.railduction.netcore.dll.Database_Attribute_System
             return BuildQuery(paramSet, paramWhere);
         }
 
+        /// <summary>
+        /// Builds an DELETE-Sql-query based on an object<para/>
+        /// Object needs to have at least 1 primary-key!
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="classObject">Given object (marked with Db-attributes)</param>
+        /// <returns>DELETE-Sql-query</returns>
         public static string DeleteByPrimaryKeys<T>(T classObject)
         {
             Type classType = classObject.GetType();
 
             // Get db-table-name from class
-            string tableName = Function.GetDbTableName(classType);
+            string tableName = DbFunction.GetDbTableName(classType);
 
             // Get class db-fields
             Dictionary<string, object> dbPrimaryKeys = new Dictionary<string, object>() { };
             Dictionary<string, object> dbAttributes = new Dictionary<string, object>() { };
             Dictionary<string, object> dbForeignKeys = new Dictionary<string, object>() { };
-            Function.ReadDbClassFields(classObject, ref dbPrimaryKeys, ref dbAttributes, ref dbForeignKeys);
+            DbFunction.ReadDbClassFields(classObject, ref dbPrimaryKeys, ref dbAttributes, ref dbForeignKeys);
+            if (dbPrimaryKeys.Count == 0) throw new InvalidOperationException($"Cannot generate SQL-Query of '{classType.Name}'. No primary-key/s found!");
 
             // Build where-parameters
-            object[] paramWhere = Function.BuildKeyEqualQuery(dbPrimaryKeys, " AND ");
+            object[] paramWhere = DbFunction.BuildKeyEqualQuery(dbPrimaryKeys, " AND ");
             // Add SQL-command part
             paramWhere[0] = $"DELETE FROM {tableName} WHERE "+ paramWhere[0];
 
@@ -90,25 +113,17 @@ namespace eu.railduction.netcore.dll.Database_Attribute_System
         /// <summary>
         /// Build an SQL-query<para/>
         /// Will build the query-string based on the <paramref name="param"/>s including serialising and escaping for SQL.<para/>
+        /// (Supported-Types: null, string, byte, int, float, double, DateTime, Guid)
         /// </summary>
         /// <param name="param">Params with alternating query-parts and objects beginning with a query-part
-        /// <para/>Example: "SELECT * FROM table WHERE id=", id, " AND name=", name</param>
+        /// <para/>Example: "SELECT * FROM table WHERE id=", id, " AND name=", name<para/>
+        /// Info: Any object[] will be opened recursively and added as <paramref name="param"/> accordingly!
+        /// </param>
         public static string BuildQuery(params object[] param)
         {
-            // Convert array to list and add object[] to it accordingly
+            // Convert array to list and add object[] to it recursively
             List<object> paramz = new List<object>() { };
-            foreach (object obj in param)
+            Function.RecursiveParameterCopying(ref paramz, (object[])param);
-            {
-                if (!(obj is object[]))
-                    paramz.Add(obj);
-                else
-                {
-                    foreach (object obj2 in (object[])obj)
-                    {
-                        paramz.Add(obj2);
-                    }
-                }
-            }
 
             string query = "";
             for (int i = 0; i < paramz.Count; i++)
@@ -125,7 +140,7 @@ namespace eu.railduction.netcore.dll.Database_Attribute_System
                     {
                         paramString = "'" + Function.SqlEscape((string)paramz[i]) + "'";  // wrap in sql-brackets and escape sql, if any
                     }
-                    else if (paramz[i].GetType() == typeof(int) || paramz[i].GetType() == typeof(float) || paramz[i].GetType() == typeof(double))  // Handle int, float & double
+                    else if (paramz[i].GetType() == typeof(byte) || paramz[i].GetType() == typeof(int) || paramz[i].GetType() == typeof(float) || paramz[i].GetType() == typeof(double))  // Handle int, float & double
                     {
                         paramString = paramz[i].ToString().Replace(",", ".");    // just format to string and form comma to sql-comma
                     }

Database-Attribute_System/internal/DbFunction.cs

@@ -6,21 +6,9 @@ using System.Text;
 
 namespace eu.railduction.netcore.dll.Database_Attribute_System
 {
-    class Function
+    class DbFunction
     {
-        public static string SqlEscape(string str)
+        internal static object[] BuildKeyEqualQuery(Dictionary<string, object> keysets, string seperator)
-        {
-            string str_cpy = str.Replace(@"'", @"\'");
-            return str_cpy;
-        }
-
-        public static string SqlSerialise(DateTime dt)
-        {
-            return dt.ToString("yyyy-MM-dd HH:mm:ss");
-        }
-
-
-        public static object[] BuildKeyEqualQuery(Dictionary<string, object> keysets, string seperator)
         {
             object[] param = new object[keysets.Count * 2];
             int c = 0;
@@ -43,18 +31,18 @@ namespace eu.railduction.netcore.dll.Database_Attribute_System
         public static string GetDbTableName(Type classType)
         {
             // Check if class has attribute 'DbObject' and get the database table-name
-            if (!(classType.GetCustomAttribute(typeof(DbObject), true) is DbObject dbObjectAttribute)) throw new InvalidOperationException("Cannot generate SQL-Query of class. Missing Attribute 'DbObject'");
+            if (!(classType.GetCustomAttribute(typeof(DbObject), true) is DbObject dbObjectAttribute)) throw new InvalidOperationException($"Cannot generate SQL-Query of '{classType.Name}'. Missing Attribute 'DbObject'");
             string tableName = dbObjectAttribute._tableName ?? classType.Name;    // If no alternative table-name is specified, use the class-name
 
             return tableName;
         }
 
-        public static void ReadDbClassFields<T>(T classObject, ref Dictionary<string, object> dbPrimaryKeys, ref Dictionary<string, object> dbAttributes, ref Dictionary<string, object> dbForeignKeys)
+        internal static void ReadDbClassFields<T>(T classObject, ref Dictionary<string, object> dbPrimaryKeys, ref Dictionary<string, object> dbAttributes, ref Dictionary<string, object> dbForeignKeys)
         {
             Type classType = typeof(T);
 
             // Reset lists (just in case)
-            dbPrimaryKeys = new Dictionary<string, object> () { };
+            dbPrimaryKeys = new Dictionary<string, object>() { };
             dbAttributes = new Dictionary<string, object>() { };
             dbForeignKeys = new Dictionary<string, object>() { };
 

Database-Attribute_System/internal/Function.cs

@@ -0,0 +1,34 @@
+using eu.railduction.netcore.dll.Database_Attribute_System.Attributes;
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Text;
+
+namespace eu.railduction.netcore.dll.Database_Attribute_System
+{
+    internal class Function
+    {
+        public static string SqlEscape(string str)
+        {
+            string str_cpy = str.Replace(@"'", @"\'");
+            return str_cpy;
+        }
+
+        public static string SqlSerialise(DateTime dt, string format = "yyyy-MM-dd HH:mm:ss")
+        {
+            return dt.ToString(format);
+        }
+
+        // Recursive object[] copying
+        internal static void RecursiveParameterCopying(ref List<object> paramz, object[] objects)
+        {
+            foreach (object obj in objects)
+            {
+                if (!(obj is object[]))
+                    paramz.Add(obj);
+                else
+                    RecursiveParameterCopying(ref paramz, (object[])obj);
+            }
+        }
+    }
+}