asp.Netmvcソース分析-editorFor

私たちのmvcの日常開発では、LabelFor、EditorFor、Editorなど、この拡張方法には似ているものがたくさんあります.ここではEditorForで話しましょう.これは比較的複雑だと思います.
まず、EditorForの定義を見てみましょう.
 public static MvcHtmlString EditorFor(this HtmlHelper html, Expression> expression, object additionalViewData) {             return TemplateHelpers.TemplateFor(html, expression, null/* templateName */, null/* htmlFieldName */, DataBoundControlMode.Edit, additionalViewData);         }
EditorForには多くの定義があるが、実際にはTemplateHelpersを呼び出す.TemplateForメソッド.
  internal static MvcHtmlString TemplateFor(this HtmlHelper html, Expression> expression,                                                                       string templateName, string htmlFieldName, DataBoundControlMode mode,                                                                       object additionalViewData) {             return MvcHtmlString.Create(TemplateFor(html, expression, templateName, htmlFieldName, mode, additionalViewData, TemplateHelper)); 今皆さんはTemplateFor方法の主なパラメータがどれらがあるか知っているでしょうが、実際の開発では私たちのtemplateName、htmlFiledName、additionalViewDataは通常nullで、modeはDataBoundControl Modeです.Edit例を挙げてみましょう
 public class UserInfo     {         [StringLength(100, MinimumLength = 10)]         [Required]         public string UserName { set; get; }     }
  @Html.EditorFor(model => model.UserName)
このコードは簡単ではありませんか.
では、TemplateForの実装を見てみましょう.
      return templateHelper(html,                                   ModelMetadata.FromLambdaExpression(expression, html.ViewData),                                   htmlFieldName ?? ExpressionHelper.GetExpressionText(expression),                                   templateName,                                   mode,                                   additionalViewData);
まずModelMetadataを見てみましょうFromLambdaExpression(expression,html.ViewData)という文は、ModelMetadataを取得する方法です.具体的には、次のようになります.

public static ModelMetadata FromLambdaExpression(Expression> expression,
                                                                             ViewDataDictionary viewData) {
            if (expression == null) {
                throw new ArgumentNullException("expression");
            }
            if (viewData == null) {
                throw new ArgumentNullException("viewData");
            }

            string propertyName = null;
            Type containerType = null;
            bool legalExpression = false;

            // Need to verify the expression is valid; it needs to at least end in something
            // that we can convert to a meaningful string for model binding purposes

            switch (expression.Body.NodeType) {
                // ArrayIndex always means a single-dimensional indexer; multi-dimensional indexer is a method call to Get()
                case ExpressionType.ArrayIndex:
                    legalExpression = true;
                    break;

                // Only legal method call is a single argument indexer/DefaultMember call
                case ExpressionType.Call:
                    legalExpression = ExpressionHelper.IsSingleArgumentIndexer(expression.Body);
                    break;

                // Property/field access is always legal
                case ExpressionType.MemberAccess:
                    MemberExpression memberExpression = (MemberExpression)expression.Body;
                    propertyName = memberExpression.Member is PropertyInfo ? memberExpression.Member.Name : null;
                    containerType = memberExpression.Expression.Type;
                    legalExpression = true;
                    break;

                // Parameter expression means "model => model", so we delegate to FromModel
                case ExpressionType.Parameter:
                    return FromModel(viewData);
            }

            if (!legalExpression) {
                throw new InvalidOperationException(MvcResources.TemplateHelpers_TemplateLimitations);
            }

            TParameter container = viewData.Model;
            Func

Editorを呼び出した場合、フォース呼び出しはFromLambdaExpressionメソッドではなくFromStringExpressionメソッドであり、この2つのメソッドの差は大きくありません.FromLambdaExpressionという方法を見てみましょう.
この図を見て、return GetMetadataFromProvider(modelAccessor,typeof(TValue)、propertyName、containerType);このコードの中のパラメータはみんな着いたと信じています.
propertyName=“UserName” containerType=MvcApp.Controllers.UserInfo,modelAccessorはインスタンスを作成し,インスタンスの作成はmodel=>modelである.UserNameという言葉.GetMetadataFromProviderという方法については何も言うことはありませんが、前の記事ではすでに述べていますが、実際にはDataAnnotationsModelMetadataインスタンスを作成しています.
エクスプレスについてはGetExpressionText(expression)という言葉は、デフォルトでは属性名を返します.具体的には、次のようになります.

  public static string GetExpressionText(LambdaExpression expression) {
            // Split apart the expression string for property/field accessors to create its name
            Stack nameParts = new Stack();
            Expression part = expression.Body;

            while (part != null) {
                if (part.NodeType == ExpressionType.Call) {
                    MethodCallExpression methodExpression = (MethodCallExpression)part;

                    if (!IsSingleArgumentIndexer(methodExpression)) {
                        break;
                    }

                    nameParts.Push(
                        GetIndexerInvocation(
                            methodExpression.Arguments.Single(),
                            expression.Parameters.ToArray()
                        )
                    );

                    part = methodExpression.Object;
                }
                else if (part.NodeType == ExpressionType.ArrayIndex) {
                    BinaryExpression binaryExpression = (BinaryExpression)part;

                    nameParts.Push(
                        GetIndexerInvocation(
                            binaryExpression.Right,
                            expression.Parameters.ToArray()
                        )
                    );

                    part = binaryExpression.Left;
                }
                else if (part.NodeType == ExpressionType.MemberAccess) {
                    MemberExpression memberExpressionPart = (MemberExpression)part;
                    nameParts.Push("." + memberExpressionPart.Member.Name);
                    part = memberExpressionPart.Expression;
                }
                else if (part.NodeType == ExpressionType.Parameter) {
                    // Dev10 Bug #907611
                    // When the expression is parameter based (m => m.Something...), we'll push an empty
                    // string onto the stack and stop evaluating. The extra empty string makes sure that
                    // we don't accidentally cut off too much of m => m.Model.
                    nameParts.Push(String.Empty);
                    part = null;
                }
                else {
                    break;
                }
            }

            // If it starts with "model", then strip that away
            if (nameParts.Count > 0 && String.Equals(nameParts.Peek(), ".model", StringComparison.OrdinalIgnoreCase)) {
                nameParts.Pop();
            }

            if (nameParts.Count > 0) {
                return nameParts.Aggregate((left, right) => left + right).TrimStart('.');
            }

            return String.Empty;
        }

ここでのループは2回実行され、1回目は実行されます.
 else if (part.NodeType == ExpressionType.MemberAccess) {                     MemberExpression memberExpressionPart = (MemberExpression)part;                     nameParts.Push("."+ memberExpressionPart.Member.Name);                     part = memberExpressionPart.Expression;                 }
2回目の実行
    else if (part.NodeType == ExpressionType.Parameter) {                    //Dev10 Bug #907611                    //When the expression is parameter based (m => m.Something...), we'll push an empty                    //string onto the stack and stop evaluating. The extra empty string makes sure that                    //we don't accidentally cut off too much of m => m.Model.                     nameParts.Push(String.Empty);                     part = null;                 }
もちろん、このメソッドのデフォルトの戻り結果はここでUserNameであり、htmlがid属性とname属性の値を生成するのがデフォルトです.
今からTemplateHelperの方法を見てみましょう

 internal static string TemplateHelper(HtmlHelper html, ModelMetadata metadata, string htmlFieldName, string templateName, DataBoundControlMode mode, object additionalViewData, ExecuteTemplateDelegate executeTemplate) {
            // TODO: Convert Editor into Display if model.IsReadOnly is true? Need to be careful about this because
            // the Model property on the ViewPage/ViewUserControl is get-only, so the type descriptor automatically
            // decorates it with a [ReadOnly] attribute...

            if (metadata.ConvertEmptyStringToNull && String.Empty.Equals(metadata.Model)) {
                metadata.Model = null;
            }

            object formattedModelValue = metadata.Model;
            if (metadata.Model == null && mode == DataBoundControlMode.ReadOnly) {
                formattedModelValue = metadata.NullDisplayText;
            }

            string formatString = mode == DataBoundControlMode.ReadOnly ? metadata.DisplayFormatString : metadata.EditFormatString;
            if (metadata.Model != null && !String.IsNullOrEmpty(formatString)) {
                formattedModelValue = String.Format(CultureInfo.CurrentCulture, formatString, metadata.Model);
            }

            // Normally this shouldn't happen, unless someone writes their own custom Object templates which
            // don't check to make sure that the object hasn't already been displayed
            object visitedObjectsKey = metadata.Model ?? metadata.RealModelType;
            if (html.ViewDataContainer.ViewData.TemplateInfo.VisitedObjects.Contains(visitedObjectsKey)) {    // DDB #224750
                return String.Empty;
            }

            ViewDataDictionary viewData = new ViewDataDictionary(html.ViewDataContainer.ViewData) {
                Model = metadata.Model,
                ModelMetadata = metadata,
                TemplateInfo = new TemplateInfo {
                    FormattedModelValue = formattedModelValue,
                    HtmlFieldPrefix = html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(htmlFieldName),
                    VisitedObjects = new HashSet

この方法は、実際には簡単であり、現在のmodelの値とhtmlを表示するformatフォーマットを取得し、最後にここでViewDataDictionaryインスタンスviewDataを新たに作成し、パラメータのadditionalViewDataもこのviewDataに統合し、現在の値(visitedObjectsKey、すなわちtextboxに最後に表示されるvalue)をviewDataのVisitedObjects属性に追加する.最後の再呼び出し
  return
executeTemplate(html, viewData, templateName, mode, GetViewNames, GetDefaultActions);方法.
では、ExecuteTemplateの方法を見てみましょう.

   internal static string ExecuteTemplate(HtmlHelper html, ViewDataDictionary viewData, string templateName, DataBoundControlMode mode, GetViewNamesDelegate getViewNames, GetDefaultActionsDelegate getDefaultActions) {
            Dictionary actionCache = GetActionCache(html);
            Dictionary> defaultActions = getDefaultActions(mode);
            string modeViewPath = modeViewPaths[mode];

            foreach (string viewName in getViewNames(viewData.ModelMetadata, templateName, viewData.ModelMetadata.TemplateHint, viewData.ModelMetadata.DataTypeName)) {
                string fullViewName = modeViewPath + "/" + viewName;
                ActionCacheItem cacheItem;

                if (actionCache.TryGetValue(fullViewName, out cacheItem)) {
                    if (cacheItem != null) {
                        return cacheItem.Execute(html, viewData);
                    }
                }
                else {
                    ViewEngineResult viewEngineResult = ViewEngines.Engines.FindPartialView(html.ViewContext, fullViewName);
                    if (viewEngineResult.View != null) {
                        actionCache[fullViewName] = new ActionCacheViewItem { ViewName = fullViewName };

                        using (StringWriter writer = new StringWriter(CultureInfo.InvariantCulture)) {
                            viewEngineResult.View.Render(new ViewContext(html.ViewContext, viewEngineResult.View, viewData, html.ViewContext.TempData, writer), writer);
                            return writer.ToString();
                        }
                    }

                    Func defaultAction;
                    if (defaultActions.TryGetValue(viewName, out defaultAction)) {
                        actionCache[fullViewName] = new ActionCacheCodeItem { Action = defaultAction };
                        return defaultAction(MakeHtmlHelper(html, viewData));
                    }

                    actionCache[fullViewName] = null;
                }
            }

            throw new InvalidOperationException(
                String.Format(
                    CultureInfo.CurrentCulture,
                    MvcResources.TemplateHelpers_NoTemplate,
                    viewData.ModelMetadata.RealModelType.FullName
                )
            );
        }

ここでのGetActionCacheの方法は、現在のcontextから簡単である.Itemsで辞書データを取得し、ない場合はインスタンス化してcontextに加える.Itemsにあります.GetDefaultActionsの方法も簡単です
  internal static Dictionary> GetDefaultActions(DataBoundControlMode mode) {
            return mode == DataBoundControlMode.ReadOnly ? defaultDisplayActions : defaultEditorActions;
        }
GetView Nameは、viewの名前を取得する方法の1つです.

 internal static IEnumerable GetViewNames(ModelMetadata metadata, params string[] templateHints) {
            foreach (string templateHint in templateHints.Where(s => !String.IsNullOrEmpty(s))) {
                yield return templateHint;
            }

            // We don't want to search for Nullable, we want to search for T (which should handle both T and Nullable)
            Type fieldType = Nullable.GetUnderlyingType(metadata.RealModelType) ?? metadata.RealModelType;

            // TODO: Make better string names for generic types
            yield return fieldType.Name;

            if (!metadata.IsComplexType) {
                yield return "String";
            }
            else if (fieldType.IsInterface) {
                if (typeof(IEnumerable).IsAssignableFrom(fieldType)) {
                    yield return "Collection";
                }

                yield return "Object";
            }
            else {
                bool isEnumerable = typeof(IEnumerable).IsAssignableFrom(fieldType);

                while (true) {
                    fieldType = fieldType.BaseType;
                    if (fieldType == null)
                        break;

                    if (isEnumerable && fieldType == typeof(Object)) {
                        yield return "Collection";
                    }

                    yield return fieldType.Name;
                }
            }
        }

デフォルト戻りパラメータ順序はtemplateHintsのviewであり、次にパラメータデータ型に基づいて対応するデフォルトviewを返す.ここで戻ってきたのはStringです.
ではExecuteTemplateメソッドに戻ります
 string fullViewName = modeViewPath + "/"+ viewName;これは私たちのビューが見つかりました.もし私たちが以前actionCacheにキーを含んでいたら、直接ビューを実行して戻り、次にView Enginesを通じて戻ります.Engines.FindPartialViewがビューを探しに来て、見つかったらビューを出力して返します.そうでなければデフォルトの処理を呼び出す
   if (defaultActions.TryGetValue(viewName, out defaultAction)) {                         actionCache[fullViewName] = new ActionCacheCodeItem { Action = defaultAction };                         return defaultAction(MakeHtmlHelper(html, viewData));                     }
ここでのdefaultAction対応はDefaultDisplayTemplates.StringTemplateは、私のviewNameがStringなので、ここでのMakeHtmlHelperメソッドは、現在のViewContextとviewDataに基づいて新しいHtmlHelperをインスタンス化します.
DefaultEditorTemplates.StringTemplateメソッドは非常に簡単です.
  return html.TextBox(String.Empty,                                 html.ViewContext.ViewData.TemplateInfo.FormattedModelValue,                                 CreateHtmlAttributes("text-box single-line")).ToHtmlString();
主にTextBoxメソッドを呼び出します.
    public static MvcHtmlString TextBox(this HtmlHelper htmlHelper, string name, object value, IDictionary htmlAttributes) {             return InputHelper(htmlHelper, InputType.Text, null, name, value, (value == null)/* useViewData */, false/* isChecked */, true/* setId */, true/* isExplicitValue */, htmlAttributes);         }

    private static MvcHtmlString InputHelper(HtmlHelper htmlHelper, InputType inputType, ModelMetadata metadata, string name, object value, bool useViewData, bool isChecked, bool setId, bool isExplicitValue, IDictionary htmlAttributes) {
            string fullName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name);
            if (String.IsNullOrEmpty(fullName)) {
                throw new ArgumentException(MvcResources.Common_NullOrEmpty, "name");
            }

            TagBuilder tagBuilder = new TagBuilder("input");
            tagBuilder.MergeAttributes(htmlAttributes);
            tagBuilder.MergeAttribute("type", HtmlHelper.GetInputTypeString(inputType));
            tagBuilder.MergeAttribute("name", fullName, true);

            string valueParameter = Convert.ToString(value, CultureInfo.CurrentCulture);
            bool usedModelState = false;

            switch (inputType) {
                case InputType.CheckBox:
                    bool? modelStateWasChecked = htmlHelper.GetModelStateValue(fullName, typeof(bool)) as bool?;
                    if (modelStateWasChecked.HasValue) {
                        isChecked = modelStateWasChecked.Value;
                        usedModelState = true;
                    }
                    goto case InputType.Radio;
                case InputType.Radio:
                    if (!usedModelState) {
                        string modelStateValue = htmlHelper.GetModelStateValue(fullName, typeof(string)) as string;
                        if (modelStateValue != null) {
                            isChecked = String.Equals(modelStateValue, valueParameter, StringComparison.Ordinal);
                            usedModelState = true;
                        }
                    }
                    if (!usedModelState && useViewData) {
                        isChecked = htmlHelper.EvalBoolean(fullName);
                    }
                    if (isChecked) {
                        tagBuilder.MergeAttribute("checked", "checked");
                    }
                    tagBuilder.MergeAttribute("value", valueParameter, isExplicitValue);
                    break;
                case InputType.Password:
                    if (value != null) {
                        tagBuilder.MergeAttribute("value", valueParameter, isExplicitValue);
                    }
                    break;
                default:
                    string attemptedValue = (string)htmlHelper.GetModelStateValue(fullName, typeof(string));
                    tagBuilder.MergeAttribute("value", attemptedValue ?? ((useViewData) ? htmlHelper.EvalString(fullName) : valueParameter), isExplicitValue);
                    break;
            }

            if (setId) {
                tagBuilder.GenerateId(fullName);
            }

            // If there are any errors for a named field, we add the css attribute.
            ModelState modelState;
            if (htmlHelper.ViewData.ModelState.TryGetValue(fullName, out modelState)) {
                if (modelState.Errors.Count > 0) {
                    tagBuilder.AddCssClass(HtmlHelper.ValidationInputCssClassName);
                }
            }

            tagBuilder.MergeAttributes(htmlHelper.GetUnobtrusiveValidationAttributes(name, metadata));

            if (inputType == InputType.CheckBox) {
                // Render an additional  for checkboxes. This
                // addresses scenarios where unchecked checkboxes are not sent in the request.
                // Sending a hidden input makes it possible to know that the checkbox was present
                // on the page when the request was submitted.
                StringBuilder inputItemBuilder = new StringBuilder();
                inputItemBuilder.Append(tagBuilder.ToString(TagRenderMode.SelfClosing));

                TagBuilder hiddenInput = new TagBuilder("input");
                hiddenInput.MergeAttribute("type", HtmlHelper.GetInputTypeString(InputType.Hidden));
                hiddenInput.MergeAttribute("name", fullName);
                hiddenInput.MergeAttribute("value", "false");
                inputItemBuilder.Append(hiddenInput.ToString(TagRenderMode.SelfClosing));
                return MvcHtmlString.Create(inputItemBuilder.ToString());
            }

            return tagBuilder.ToMvcHtmlString(TagRenderMode.SelfClosing);
        }

ここのInputHelperはhtml文字列を本当に生成する場所です.この方法は全体的にわかりやすいですが、この方法にはこうあることに注意してください.
            tagBuilder.MergeAttributes(htmlHelper.GetUnobtrusiveValidationAttributes(name, metadata));
これは、図のようなオブジェクト上の検証プロパティを処理することです.
皆さんはここまでEditorForの方法について知っていると思いますが、複雑な感じがします.