Add project files.

Model/ColumnCollection.cs

@@ -0,0 +1,59 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace DbTools.Model {
+    internal class ColumnCollection {
+        internal Dictionary<string, string> Items { get; private set; } = new Dictionary<string, string>();
+
+        public ColumnCollection() {
+            Items = new Dictionary<string, string>();
+        }
+
+        public string this[string columnName] {
+            get {
+                if (Items.ContainsKey(columnName)) {
+                    return Items[columnName];
+                }
+                return null;
+            }
+            set {
+                if (Items.ContainsKey(columnName)) {
+                    Items[columnName] = value;
+                } else {
+                    Items.Add(columnName, value);
+                }
+            }
+        }
+
+        public void Add(string columnName, string columnDefinition) {
+            if (!Items.ContainsKey(columnName)) {
+                Items.Add(columnName, columnDefinition);
+            }
+        }
+
+        public bool Contains(string columnName) {
+            return Items.ContainsKey(columnName);
+        }
+
+        public string[] GetColumnNames() {
+            return Items.Keys.ToArray();
+        }
+
+        public int Count() {
+            return Items.Count;
+        }
+
+        public void Clear() {
+            Items.Clear();
+        }
+
+        public override string ToString() {
+            StringBuilder sb = new StringBuilder();
+            foreach (var kvp in Items) {
+                sb.AppendLine($"{kvp.Key}: {kvp.Value}");
+            }
+            return sb.ToString();
+        }
+    }
+}