Accessing C# property name or attributes

Question

I would like to automatically generate SQL statements from a class instance. The method should look like Update(object[] Properties, object PrimaryKeyProperty). The method is pa

Answer 1

Let's say (from the first sample, method update of a class MyClass):

public class MyClass {

public int iMyStatusProperty { get; set; }
public int iMyKey { get; set; }

public int UpdateStatusProperty(int iValue){
this.iMyStatusProperty = iValue;
return _Update( new[iMyStatusProperty ], iMyKey); // this should generate SQL: "UPDATE MyClass set iMyStatusProperty = {iMyStatusProperty} where iMyKey = {iMyKey}"
}

{iMyStatusProperty} and {iMyKey} are property values of a class instance.

So, the problem is how to get property name (reflection) from a property without using names of properties as strings (to avoid field name typos).

Answer 2

You can do something like this:

Type t = someInstance.getType();

foreach (MemberInfo mi in t.GetMembers())
{
    if (mi.MemberType == MemberTypes.Property)
    {
        Console.WriteLine(mi.Name);
    }
}

to get all the property names for instance's type.

Answer 3

I found a perfect solution in This Post

public static string GetPropertyName<T>(Expression<Func<T>> propertyExpression)
{
   return (propertyExpression.Body as MemberExpression).Member.Name;
}

And then for the usage :

var propertyName = GetPropertyName(
() => myObject.AProperty); // returns "AProperty"

Works like a charm

Answer 4

Not 100% sure if this will get you what you're looking for, this will fetch all properties with [Column] attribute inside your class: In the datacontext I have:

 public ReadOnlyCollection<MetaDataMember> ColumnNames<TEntity>( )
    {
        return this.Mapping.MappingSource.GetModel(typeof(DataContext)).GetMetaType(typeof(TEntity)).DataMembers;
    }

Fetching the table column-names that are properties inside the class:

       MyDataContext db = GetDataContext(); 
       var allColumnPropertyNames =   db.ColumnNames<Animal>().Where(n => n.Member.GetCustomAttributes(typeof(System.Data.Linq.Mapping.ColumnAttribute), false).FirstOrDefault() != null).Select(n => n.Name);

Answer 5

Just wrote an implementation of this for a presentation on lambdas for our usergroup last Tuesday.

• You can do

  MembersOf<Animal>.GetName(x => x.Status)

• Or

  var a = new Animal() a.MemberName(x => x.Status)

the code:

public static class MembersOf<T> {
    public static string GetName<R>(Expression<Func<T,R>> expr) {
        var node = expr.Body as MemberExpression;
        if (object.ReferenceEquals(null, node)) 
            throw new InvalidOperationException("Expression must be of member access");
        return node.Member.Name;
    }
}

• Link to the presentation and code samples.
• Also in SVN (more likely to be updated): http://gim-projects.googlecode.com/svn/presentations/CantDanceTheLambda

Answer 6

Since you already have an explicit handle to the specific property you want, you know the name - can you just type it?