Change Output format to match PR feedback

Don't use Environment.Exit()

PR Feedback, Unecessary Usings and Immutable types

tools/MultiProjectValidator/AnalysisRules/DependencyMismatch/DependencyGroup.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+
+namespace ProjectSanity.AnalysisRules.DependencyMismatch
+{
+    internal class DependencyGroup
+    {
+        public static DependencyGroup CreateWithEntry(DependencyInfo dependencyInfo)
+        {
+            var dependencyGroup = new DependencyGroup
+            {
+                DependencyName = dependencyInfo.Name,
+                VersionDependencyInfoMap = new Dictionary<string, List<DependencyInfo>>()
+            };
+
+            dependencyGroup.AddEntry(dependencyInfo);
+
+            return dependencyGroup;
+        }
+
+        public string DependencyName { get; private set; }
+        public Dictionary<string, List<DependencyInfo>> VersionDependencyInfoMap { get; private set; }
+
+        public bool HasConflict
+        {
+            get
+            {
+                return VersionDependencyInfoMap.Count > 1;
+            }
+        }
+
+        public void AddEntry(DependencyInfo dependencyInfo)
+        {
+            if (!dependencyInfo.Name.Equals(DependencyName, StringComparison.OrdinalIgnoreCase))
+            {
+                throw new Exception("Added dependency does not match group");
+            }
+
+            if (VersionDependencyInfoMap.ContainsKey(dependencyInfo.Version))
+            {
+                VersionDependencyInfoMap[dependencyInfo.Version].Add(dependencyInfo);
+            }
+            else
+            {
+                VersionDependencyInfoMap[dependencyInfo.Version] = new List<DependencyInfo>()
+                {
+                    dependencyInfo
+                };
+            }
+        }
+
+    }
+}