come creare un helper HTML per estendere TextBoxFor() per aggiungere lo stile CSS?

Question

come creare un helper HTML per estendere TextBoxFor() per aggiungere lo stile CSS?

@Html.TextBoxFor(model => model.FirstName, new { @class = "txt" }) 

Answer 1

public static System.Web.Mvc.MvcHtmlString DtxTextBoxFor<TModel, TValue> 
     (this System.Web.Mvc.HtmlHelper<TModel> html, 
     System.Linq.Expressions.Expression<System.Func<TModel, TValue>> expression, 
     System.Collections.Generic.IDictionary<string, object> htmlAttributes = null, bool readOnly = false) 
    { 
     if (htmlAttributes == null) 
     { 
      htmlAttributes = 
       new System.Collections.Generic.Dictionary<string, object>(); 
     } 

     System.Web.Mvc.ModelMetadata oModelMetadata = 
      System.Web.Mvc.ModelMetadata.FromLambdaExpression(expression, html.ViewData); 

     if (oModelMetadata == null) 
     { 
      if (readOnly) 
      { 
       if (htmlAttributes.ContainsKey("readonly") == false) 
       { 
        htmlAttributes.Add("readonly", "read-only"); 
       } 
      } 
     } 
     else 
     { 
      if (htmlAttributes.ContainsKey("placeholder") == false) 
      { 
       string strHtmlFieldName = 
        System.Web.Mvc.ExpressionHelper.GetExpressionText(expression); 

       string strLabelText = 
        oModelMetadata.DisplayName ?? 
        oModelMetadata.PropertyName ?? 
        strHtmlFieldName.Split('.').Last(); 

       if (string.IsNullOrEmpty(strLabelText) == false) 
       { 
        htmlAttributes.Add("placeholder", strLabelText); 
       } 
      } 

      if ((readOnly) || (oModelMetadata.IsReadOnly)) 
      { 
       if (htmlAttributes.ContainsKey("readonly") == false) 
       { 
        htmlAttributes.Add("readonly", "read-only"); 
       } 
      } 
     } 

     htmlAttributes.Add("class", "form-control"); 

     System.Linq.Expressions.MemberExpression oMemberExpression = 
      expression.Body as System.Linq.Expressions.MemberExpression; 

     if (oMemberExpression != null) 
     { 
      System.ComponentModel.DataAnnotations.StringLengthAttribute oStringLengthAttribute = 
       oMemberExpression.Member.GetCustomAttributes 
       (typeof(System.ComponentModel.DataAnnotations.StringLengthAttribute), false) 
       .FirstOrDefault() as System.ComponentModel.DataAnnotations.StringLengthAttribute; 

      if (oStringLengthAttribute != null) 
      { 
       if (htmlAttributes.ContainsKey("maxlength") == false) 
       { 
        htmlAttributes.Add("maxlength", oStringLengthAttribute.MaximumLength); 
       } 
      } 
     } 

     return (html.TextBoxFor(expression, htmlAttributes)); 
    } 

Answer 2

Hai solo bisogno di creare un extension method su HtmlHelper:

public static class MyHtmlHelpers 
{ 
    public static MvcHtmlString MyTextBoxFor<TModel, TProperty>(
     this HtmlHelper<TModel> helper, 
     Expression<Func<TModel, TProperty>> expression) 
    { 
     return helper.TextBoxFor(expression, new { @class = "txt" }); 
    } 
} 

Poi a suo avviso è possibile utilizzarlo come:

@Html.MyTextBoxFor(model => model.FirstName) 

Nota: Non dimenticare di @using il namespace di MyHtmlHelpers se le vostre opinioni.

Answer 3

Sulla base di @nemesv la risposta è un'estensione che supporta htmlAttributes con attributi personalizzati aggiuntivi.

vb.net:

<Extension()> 
Function MyTextBoxFor(Of TModel, TProperty)(ByVal helper As HtmlHelper(Of TModel), ByVal expression As Expression(Of Func(Of TModel, TProperty)), htmlAttributes As Object) As MvcHtmlString   
    'copy htmlAttributes object to Dictionary 
    Dim dicHtmlAttributes As New Dictionary(Of String, Object) 
    For Each prop in htmlAttributes.GetType().GetProperties() 
     dicHtmlAttributes.Add(prop.Name,prop.GetValue(htmlAttributes)) 
    Next 
    'add custom attribute 
    dicHtmlAttributes.Add("foo","bar") 

    Return helper.TextBoxFor(expression, dicHtmlAttributes) 
End Function 

C#:

public static MvcHtmlString MyTextBoxFor<TModel, TProperty>(
    this HtmlHelper<TModel> helper, 
    Expression<Func<TModel, TProperty>> expression, object htmlAttributes) 
{ 
    //copy htmlAttributes object to Dictionary 
    Dictionary<string, object> dicHtmlAttributes = new Dictionary<string, object>; 
    foreach (var prop in htmlAttributes.GetType().GetProperties()) 
    { 
     dicHtmlAttributes.Add(prop.Name, prop.GetValue(htmlAttributes)); 
    } 
    //add custom attribute 
    dicHtmlAttributes.Add("foo", "bar"); 
    return helper.TextBoxFor(expression, dicHtmlAttributes); 
}