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maxlength attribute of a text box from the DataAnnotations StringLength in Asp.Net MVC

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攒了一身酷
攒了一身酷 2020-11-30 18:33

I am working on an MVC2 application and want to set the maxlength attributes of the text inputs.

I have already defined the stringlength attribute on the Model objec

7条回答
  • 萌比男神i
    萌比男神i (楼主)
    2020-11-30 19:08

    I use the CustomModelMetaDataProvider to achieve this

    Step 1. Add New CustomModelMetadataProvider class

    public class CustomModelMetadataProvider : DataAnnotationsModelMetadataProvider
{   
    protected override ModelMetadata CreateMetadata(
        IEnumerable attributes,
        Type containerType,
        Func modelAccessor,
        Type modelType,
        string propertyName)
    {
        ModelMetadata metadata = base.CreateMetadata(attributes,
            containerType,
            modelAccessor,
            modelType,
            propertyName);

        //Add MaximumLength to metadata.AdditionalValues collection
        var stringLengthAttribute = attributes.OfType().FirstOrDefault();
        if (stringLengthAttribute != null)
            metadata.AdditionalValues.Add("MaxLength", stringLengthAttribute.MaximumLength);

        return metadata;
    }
}



    Step 2. In Global.asax Register the CustomModelMetadataProvider 
    


    protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    RegisterRoutes(RouteTable.Routes);
    ModelMetadataProviders.Current = new CustomModelMetadataProvider();
}

    


    Step 3. In Views/Shared/EditorTemplates Add a partial view called String.ascx
    


    <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %>
<%if (!ViewData.ModelMetadata.AdditionalValues.ContainsKey("MaxLength")) { %>
    <%: Html.TextBox("", ViewData.TemplateInfo.FormattedModelValue,  new { @class = "text-box single-line" }) %>
<% } else {
    int maxLength = (int)ViewData.ModelMetadata.AdditionalValues["MaxLength"];
    %>
    <%: Html.TextBox("", ViewData.TemplateInfo.FormattedModelValue, new { @class = "text-box single-line", MaxLength = maxLength  })%>
<% } %>

    


    Done... 
    


    Edit. The Step 3 can start to get ugly if you want to add more stuff to the textbox. If this is your case you can do the following:
    


    <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %>
<%
    IDictionary Attributes = new Dictionary();
    if (ViewData.ModelMetadata.AdditionalValues.ContainsKey("MaxLength")) {
        Attributes.Add("MaxLength", (int)ViewData.ModelMetadata.AdditionalValues["MaxLength"]);
    }
    if (ViewData.ContainsKey("style")) {
        Attributes.Add("style", (string)ViewData["style"]);
    }
    if (ViewData.ContainsKey("title")) {
        Attributes.Add("title", (string)ViewData["title"]);
    }
%>
<%: Html.TextBox("", ViewData.TemplateInfo.FormattedModelValue, Attributes)%>

    
    
    
             
    
                                                        
    
            
            
    
              
                
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