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POCustom dynamic dataannotation for field visibility c#
 

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  1. POCustom dynamic dataannotation for field visibility c#
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    <p>I am trying to create a dataannotations attribute that controls field visiblity based on settings in a database. The attribute will be used within a system that will be used by multiple clients. Further, the visibility of the field needs to be able to change on the fly. I know I could do an if statement around each field in the view, but I am trying to avoid that and keep the visibility control within the view model as follows:</p> <pre><code>[Visible(FirstName)] public string FirstName { get; set; } </code></pre> <p>I have tried creating this custom attribute that gets the value from a method from a resource class called ResourceType (which is generated using T4 and contains the necessary code to hit the database):</p> <pre><code>public class VisibleAttribute : Attribute, IMetadataAware { /// &lt;summary&gt; /// Whether this field is visible /// &lt;/summary&gt; public bool Hidden { get; set; } public VisibleAttribute(string theFieldName) { ResourceType resources = new ResourceType(); Type _resourceType = typeof(ResourceType); MethodInfo getHidden = _resourceType.GetMethod("IsHidden"); object[] requiredParams = new object[] { theFieldName }; Hidden = (bool)getHidden.Invoke(resources, requiredParams); } public void OnMetadataCreated(ModelMetadata metadata) { metadata.ShowForEdit = !Hidden; metadata.HideSurroundingHtml = Hidden; } } </code></pre> <p>Here is an excerpt of the ResourceType class:</p> <pre><code>public class ResourceType { public const string Creditors_SecondaryCreditorsPayOffYesNo_Require = "Prop_Creditors_SecondaryCreditorsPayOffYesNo_Require"; public static string Prop_FieldName_Require { get { return GetHiddenOption(FieldName) ? "true" : "false"; } } internal static bool GetHiddenOption(string fieldName) { &lt; &lt; Logic here to get the option from the database &gt; &gt; } </code></pre> <p>I have also tried the same attribute but with the following constructor:</p> <pre><code>public VisibleAttribute(string theFieldName) { ResourceType resources = new ResourceType(); Type _resourceType = typeof(ResourceType); PropertyInfo getHidden = _resourceType.GetProperty(theFieldName); Hidden = (bool)getHidden.GetValue } </code></pre> <p>The problem I have with these two attempts is that, since the code is in the constructor, it only runs the first time I load the page after an IIS reset. So, any further changes I make to the visibility settings are not reflected without amother IIS reset.</p> <p>I also tried creating a custom DataAnnotationsModelMetadataProvider that attempts to only load the setting once per page request:</p> <pre><code>public class EGTDataAnnotationsModelMetadataProvider : DataAnnotationsModelMetadataProvider { protected override ModelMetadata CreateMetadata(IEnumerable&lt;Attribute&gt; attributes, Type containerType, Func&lt;object&gt; modelAccessor, Type modelType, string propertyName) { var data = base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName); var visibleAttributeMetadata = attributes.SingleOrDefault(a =&gt; typeof(VisibleAttribute) == a.GetType()); if (visibleAttributeMetadata != null) { VisibleAttribute visibleAttribte = (VisibleAttribute)visibleAttributeMetadata; if (!visibleAttribte.VisibleIsSet) { PropertyInfo getHidden = visibleAttribte.ResourceType.GetProperty("Prop_" + WebUtils.RemoveSectionNameSpace(visibleAttribte.SectionName) + "_" + visibleAttribte.FieldName + "_Hide"); visibleAttribte.IsHidden = bool.Parse(getHidden.GetValue(null, null).ToString()); data.HideSurroundingHtml = visibleAttribte.IsHidden; data.ShowForEdit = !visibleAttribte.IsHidden; visibleAttribte.VisibleIsSet = true; } else { data.HideSurroundingHtml = visibleAttribte.IsHidden; data.ShowForEdit = !visibleAttribte.IsHidden; } } return data; } } </code></pre> <p>One issue I have with the ModelMetadataProvider is that the CreateMetadata method runs many times for a single field during a single request. It is very inefficient code, and a huge decrease in performace, to call the database 5-10+ times per request to get a setting that has not changed since the beginning of the request. If I try to set a flag indicating I've already loaded the setting, I'm back to the same scenario as above where I don't see the setting change until after an IIS reset.</p> <p>I'm hoping someone can give me some pointers as to what methods I can employ to see the database changes real time. Or am I trying to do the impossible? Thanks in advance.</p>
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