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POGet [DisplayName] attribute of a property in strongly-typed way
 

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  1. POGet [DisplayName] attribute of a property in strongly-typed way
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    <p>Good day!</p> <p>I've such method to get <code>[DisplayName]</code> attribute value of a property (which is attached directly or using <code>[MetadataType]</code> attribute). I use it in rare cases where I need to get <code>[DisplayName]</code> in controller code.</p> <pre><code>public static class MetaDataHelper { public static string GetDisplayName(Type dataType, string fieldName) { // First look into attributes on a type and it's parents DisplayNameAttribute attr; attr = (DisplayNameAttribute)dataType.GetProperty(fieldName).GetCustomAttributes(typeof(DisplayNameAttribute), true).SingleOrDefault(); // Look for [MetadataType] attribute in type hierarchy // http://stackoverflow.com/questions/1910532/attribute-isdefined-doesnt-see-attributes-applied-with-metadatatype-class if (attr == null) { MetadataTypeAttribute metadataType = (MetadataTypeAttribute)dataType.GetCustomAttributes(typeof(MetadataTypeAttribute), true).FirstOrDefault(); if (metadataType != null) { var property = metadataType.MetadataClassType.GetProperty(fieldName); if (property != null) { attr = (DisplayNameAttribute)property.GetCustomAttributes(typeof(DisplayNameAttribute), true).SingleOrDefault(); } } } return (attr != null) ? attr.DisplayName : String.Empty; } } </code></pre> <p>It works, but it has two drawbacks:</p> <ul> <li>It requires field name as string</li> <li>It doesn't work if I want to get property of a property</li> </ul> <p>Is it possible to overcome both problems using lambdas, something like we have in ASP.NET MVC:</p> <pre><code>Html.LabelFor(m =&gt; m.Property.Can.Be.Very.Complex.But.Strongly.Typed); </code></pre> <p><strong>Update</strong></p> <p>Here is an updated and checked version from <em>BuildStarted</em> solution. It is modified to use <code>DisplayName</code> attribute (you can modify back to <code>Display</code> attribute if you use it). And fixed minor bugs to get attribute of nested properties.</p> <pre><code>public static string GetDisplayName&lt;TModel&gt;(Expression&lt;Func&lt;TModel, object&gt;&gt; expression) { Type type = typeof(TModel); string propertyName = null; string[] properties = null; IEnumerable&lt;string&gt; propertyList; //unless it's a root property the expression NodeType will always be Convert switch (expression.Body.NodeType) { case ExpressionType.Convert: case ExpressionType.ConvertChecked: var ue = expression.Body as UnaryExpression; propertyList = (ue != null ? ue.Operand : null).ToString().Split(".".ToCharArray()).Skip(1); //don't use the root property break; default: propertyList = expression.Body.ToString().Split(".".ToCharArray()).Skip(1); break; } //the propert name is what we're after propertyName = propertyList.Last(); //list of properties - the last property name properties = propertyList.Take(propertyList.Count() - 1).ToArray(); //grab all the parent properties foreach (string property in properties) { PropertyInfo propertyInfo = type.GetProperty(property); type = propertyInfo.PropertyType; } DisplayNameAttribute attr; attr = (DisplayNameAttribute)type.GetProperty(propertyName).GetCustomAttributes(typeof(DisplayNameAttribute), true).SingleOrDefault(); // Look for [MetadataType] attribute in type hierarchy // http://stackoverflow.com/questions/1910532/attribute-isdefined-doesnt-see-attributes-applied-with-metadatatype-class if (attr == null) { MetadataTypeAttribute metadataType = (MetadataTypeAttribute)type.GetCustomAttributes(typeof(MetadataTypeAttribute), true).FirstOrDefault(); if (metadataType != null) { var property = metadataType.MetadataClassType.GetProperty(propertyName); if (property != null) { attr = (DisplayNameAttribute)property.GetCustomAttributes(typeof(DisplayNameAttribute), true).SingleOrDefault(); } } } return (attr != null) ? attr.DisplayName : String.Empty; } </code></pre>
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    1. COYes you can. Instead of getting a string parameter in your method, use an Expression<Func<object>> parameter. From there you can read the expression for the members ("property.Can.Be.Very.Complex.But.Strongly.Typed") and use reflection to get the attribute value.
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      1. USFabian Nicollier
    2. COHave a look at `ModelMetadata` and `ModelMetadata.FromLambdaExpression()`. These places have all the metadata you need.
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      1. USDaniel A. White
    3. COCan I use it from controller or viewmodel classes? It seems to be a static method?
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