Having this simple class:
public class Book { [DataMember] [Column("Bok_Name")] [Author("AuthorName")] public string Name{ get; set; } [DataMember] [Column("Bok_Publisher")] public string Publisher{ get; set; } } How can i can get the PropertyInfo from a property knowing that the attribute type is Column and the value is Bok_Name. I has trying to do this with a linq query.
Using reflection and the .NET extension CustomAttributeExtensions.GetCustomAttribute{T} method, you can find the properties with the custom attribute. In this case, the custom attribute is from System.ComponentModel.DataAnnotations.Schema.ColumnAttribute.
var book = new Book { Name = "Jitterbug Perfume" }; PropertyInfo bokName = typeof(Book) .GetProperties(BindingFlags.Public | BindingFlags.Instance) // add other bindings if needed .FirstOrDefault(x => x.GetCustomAttribute<ColumnAttribute>() != null && x.GetCustomAttribute<ColumnAttribute>().Name.Equals("Bok_Name", StringComparison.OrdinalIgnoreCase)); // the above query only gets the first property with Column attribute equal to "Bok_Name" // if there are more than one, then use a .Where clause instead of FirstOrDefault. if (bokName != null) { string name = bokName.GetValue(book).ToString(); // do other stuff } 
var type = typeof (Book); //or var type=instance.GetType(); var res=type.GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic) .Where( p => (p.GetCustomAttribute<ColumnAttribute>() ?? new ColumnAttribute()).Value == "Bok_Name"); 
GetCustomAttribute is an extension method, so you need to add using System.Reflection; for this to work.In the piggy bank, variant on VB NET:
Dim maxLength = ValToInt(document.GetDataAnnotationPropertyAttributeValue(fieldName, GetType(MaxLengthAttribute))) Public Function GetDataAnnotationPropertyAttributeValue(propertyName As String, attributeType As Type) As Object Dim properties = Me.GetType().GetProperties() Dim propertyInfo = properties.FirstOrDefault(Function(p) p.Name?.ToLower() = propertyName?.ToLower()) If propertyInfo Is Nothing Then Return Nothing Dim attribute = propertyInfo.CustomAttributes.FirstOrDefault(Function(a) a.AttributeType.Equals(attributeType)) Return attribute?.ConstructorArguments(0).Value End Function 
