Fix SD-1718 - Post build events not added to end of project file.

src/Main/Base/Project/Src/Project/MSBuildBasedProject.cs

@@ -839,18 +839,50 @@ namespace ICSharpCode.SharpDevelop.Project
 					}
 				}
 			}
-			foreach (var propertyGroup in targetProject.PropertyGroups) {
-				if (propertyGroup.Condition == groupCondition) {
-					propertyGroup.AddProperty(propertyName, newValue);
-					return;
-				}
+			
+			var matchedPropertyGroup = FindPropertyGroup(targetProject, groupCondition, position);
+			if (matchedPropertyGroup != null) {
+				matchedPropertyGroup.AddProperty(propertyName, newValue);
+				return;
 			}
 			
-			var newGroup = targetProject.AddPropertyGroup();
+			var newGroup = AddNewPropertyGroup(targetProject, position);
 			newGroup.Condition = groupCondition;
 			newGroup.AddProperty(propertyName, newValue);
 		}
 		
+		ProjectPropertyGroupElement FindPropertyGroup(ProjectRootElement targetProject, string groupCondition, PropertyPosition position)
+		{
+			ProjectPropertyGroupElement matchedPropertyGroup = null;
+			foreach (var projectItem in targetProject.Children) {
+				ProjectPropertyGroupElement propertyGroup = projectItem as ProjectPropertyGroupElement;
+				if (propertyGroup != null) {
+					if (propertyGroup.Condition == groupCondition) {
+						matchedPropertyGroup = propertyGroup;
+						if (position != PropertyPosition.UseExistingOrCreateAfterLastImport) {
+							return matchedPropertyGroup;
+						}
+					}
+				}
+				if (position == PropertyPosition.UseExistingOrCreateAfterLastImport) {
+					if (projectItem is ProjectImportElement) {
+						matchedPropertyGroup = null;
+					}
+				}
+			}
+			return matchedPropertyGroup;
+		}
+		
+		ProjectPropertyGroupElement AddNewPropertyGroup(ProjectRootElement targetProject, PropertyPosition position)
+		{
+			if (position == PropertyPosition.UseExistingOrCreateAfterLastImport) {
+				var propertyGroup = targetProject.CreatePropertyGroupElement();
+				targetProject.AppendChild(propertyGroup);
+				return propertyGroup;
+			}
+			return targetProject.AddPropertyGroup();
+		}
+		
 		/// <summary>
 		/// Removes the property from all configurations and platforms.
 		/// </summary>