I have a project in which I have to get all the variables from a struct in a different class and add all their names to a combo box in a form. My primary issue at the moment is iterating through the struct in a way that I can add each variable individually to the combo box. I tried doing this:
msgVars vars = new msgVars();
foreach (object obj in vars)
{
comboBox1.Items.Add(GetName(obj));
}
but as you probably know, you can't iterate through a struct that way. Is there any way I can do this without hardcoding the variables in?
Also, for reference, this is the GetName function:
static string GetName<T>(T item) where T : struct
{
var properties = typeof(T).GetProperties();
if (properties.Length == 1)
{
return properties[0].Name;
}
else
{
return null;
}
}
If you are looking for a way to access properties of a struct (or class) at runtime without predefining in code that set of properties, what you probably need to use is reflection.
Here's an example:
struct MyStruct
{
private readonly int m_Age;
private readonly string m_LastName;
private readonly string m_FirstName;
public int Age { get { return m_Age; } }
public string LastName { get { return m_LastName; } }
public string FirstName { get { return m_FirstName; } }
public MyStruct( int age, string last, string first )
{
m_Age = age;
m_LastName = last;
m_FirstName = first;
}
}
class StructReflection
{
public static void Main(string[] args)
{
var theStruct = new MyStruct( 40, "Smith", "John" );
PrintStructProperties( theStruct );
}
public static void PrintStructProperties( MyStruct s )
{
// NOTE: This code will not handle indexer properties...
var publicProperties = s.GetType().GetProperties();
foreach (var prop in publicProperties)
Console.WriteLine( "{0} = {1}", prop.Name, prop.GetValue( s, null ) );
}
}
You could try using Reflection. How about storing the information in a Hashtable.
public Hashtable GetPropertyInfo(Person person)
{
var properties = new Hashtable();
PropertyInfo[] propInfo = person.GetType().GetProperties();
foreach (PropertyInfo prop in propInfo)
{
properties.Add(prop.Name, prop.GetValue(person, null));
}
return properties;
}
Then you could write the information out via:
var person = new Person()
Person.Name = "Test";
Person.Age = 21;
var PropertyInfo = GetPropertyInfo(person);
foreach (string key in PropertyInfo.Keys)
{
Console.WriteLine("{0} = {1}", key, PropertyInfo[key]);
}
A struct is a single entity, not a collection of variables. This means that you can't 'iterate' over its properties. What you need to do is get a collection of the property names and iterate over it. Your GetName function can't do this because it just returns the name of the first property.
To add the property names to a combo all you have to do is:
var vars = new msgVars();
foreach(var name in GetNames(vars))
comboBox1.Items.Add(name);
In fact, getting the property name is so easy that you could get rid of GetNames completley and just write
foreach (var prop in typeof(msgVars).GetProperties())
comboBox1.Items.Add(prop.Name);
There are various ways you can write GetNames to return a collection of names. You can fill a List with the property names although the simplest is to have it return an iterator like this:
public static IEnumerable<string> GetNames<T>(T obj) where T:struct
{
var properties = typeof (T).GetProperties();
foreach (var propertyInfo in properties)
{
yield return propertyInfo.Name;
}
}
Finally, you don't really need to pass an instance of your struct to the method, as you are enumerating the structs property names, not their values. You can rewrite GetNames like this
public static IEnumerable<string> GetNames<T>() where T:struct
{
var properties = typeof (T).GetProperties();
foreach (var propertyInfo in properties)
{
yield return propertyInfo.Name;
}
}
and load the names like this
foreach(var name in GetNames<msgVars>())
comboBox1.Items.Add(name);
Related
I am using VS2010 and EF4.0. The goal is to select fields of any IEnumerable, in order to show in the DataGridView. Take Northwind.Employees as example, the following code is OK.
private void button1_Click(object sender, EventArgs e)
{
NorthwindEntities en = new NorthwindEntities();
dataGridView1.DataSource = SelectNew(en.Employees, new string[] { "EmployeeID", "FirstName" });
}
public object SelectNew(object items, string[] fields)
{
IEnumerable<Employee> ems = items as IEnumerable<Employee>;
return ems.Select(em => new
{
id = em.EmployeeID,
name = em.FirstName
}
).ToArray();
}
The parameter object items is IEnumerable of EntityObject, and the function will be executed at client side memorry and shall have nothing to do with database now.
But I don't know the EntityObject type (Employee) until runtime, so maybe some complex reflection will be used.
I have checked this,
but when I bind the result to the control, it showed only blank rows without any column or data. And the funciton is for IQueryable, I have tried IEnumerable.AsQueryable and pass to it, but the results did not show any column either.
I've modified the example I pointed to in my comment above. This actually returns an IEnumerable<Dictionary<string,object>>, where each Dictionary represents one of the "new objects", and each key value pair in the dictionary represents a property and its value. Perhaps you can modify this for your use?
I'm not sure if you can simply bind the result to the DataGrid, but you should be able to figure it out.
I don't believe it's possible to create an anonymous type on the fly... But it might be possible to change this to use a dynamic type like ExpandoObject instead of a Dictionary. See this question for some hints on how to do that. I've never used dynamic objects, so you're on your own there!
public class TestClassA {
public string SomeString { get; set; }
public int SomeInt { get; set; }
public TestClassB ClassB { get; set; }
}
public class TestClassB {
public string AnotherString { get; set; }
}
public class Program {
private static void Main(string[] args) {
var items = new List<TestClassA>();
for (int i = 0; i < 9; i++) {
items.Add(new TestClassA {
SomeString = string.Format("This is outer string {0}", i),
SomeInt = i,
ClassB = new TestClassB { AnotherString = string.Format("This is inner string {0}", i) }
});
}
var newEnumerable = SelectNew(items, new string[] { "ClassB.AnotherString" });
foreach (var dict in newEnumerable) {
foreach (var key in dict.Keys)
Console.WriteLine("{0}: {1}", key, dict[key]);
}
Console.ReadLine();
}
public static IEnumerable<Dictionary<string, object>> SelectNew<T>(IEnumerable<T> items, string[] fields) {
var newItems = new List<Dictionary<string, object>>();
foreach (var item in items) {
var dict = new Dictionary<string, object>();
foreach (var field in fields)
dict[field] = GetPropertyValue(field, item);
newItems.Add(dict);
}
return newItems;
}
private static object GetPropertyValue(string property, object o) {
if (property == null)
throw new ArgumentNullException("property");
if (o == null)
throw new ArgumentNullException("o");
Type type = o.GetType();
string[] propPath = property.Split('.');
var propInfo = type.GetProperty(propPath[0]);
if (propInfo == null)
throw new Exception(String.Format("Could not find property '{0}' on type {1}.", propPath[0], type.FullName));
object value = propInfo.GetValue(o, null);
if (propPath.Length > 1)
return GetPropertyValue(string.Join(".", propPath, 1, propPath.Length - 1), value);
else
return value;
}
}
I want to make a C# Dictionary in which the key is the string name of a static property in a class and the value is the value of the property. Given a static property in the class called MyResources.TOKEN_ONE, how can I get the at the name of the property rather than its value? I only care about the end part of the property name (e.g. "TOKEN_ONE").
I've edited this to mention that I don't want to map all property values in the Dictionary, just a small subset of everything that's in the class. So assume that I want to get the name for a single property. Given MyResources.TOKEN_ONE, I want to get back "MyResources.TOKEN_ONE" or just "TOKEN_ONE".
Here's some sample code that shows what I'm trying to do. I need the property name because I'm trying to generate a javascript variable in which I map the property name to the variable name and the property value to the variable value. For example, I want the C# Dictionary to generate lines like the one below:
var TOKEN_ONE = "One";
using System;
using System.Collections.Generic;
namespace MyConsoleApp
{
class Program
{
static void Main(string[] args)
{
Dictionary<String, String> kvp = new Dictionary<String, String>();
// How can I use the name of static property in a class as the key for the dictionary?
// For example, I'd like to do something like the following where 'PropertyNameFromReflection'
// is a mechanism that would return "MyResources.TOKEN_ONE"
kvp.Add(MyResources.TOKEN_ONE.PropertyNameFromReflection, MyResources.TOKEN_ONE);
kvp.Add(MyResources.TOKEN_TWO.PropertyNameFromReflection, MyResources.TOKEN_TWO);
Console.ReadLine();
}
}
public static class MyResources
{
public static string TOKEN_ONE
{
get { return "One"; }
}
public static string TOKEN_TWO
{
get { return "Two"; }
}
}
}
If all you want is just to be able to refer to a single, specific property in one place in the code without having to refer to it by a literal string, then you can use an expression tree. For example, the following code declares a method that turns such an expression tree into a PropertyInfo object:
public static PropertyInfo GetProperty(Expression<Func<string>> expr)
{
var member = expr.Body as MemberExpression;
if (member == null)
throw new InvalidOperationException("Expression is not a member access expression.");
var property = member.Member as PropertyInfo;
if (property == null)
throw new InvalidOperationException("Member in expression is not a property.");
return property;
}
Now you can do something like this:
public void AddJavaScriptToken(Expression<Func<string>> propertyExpression)
{
var p = GetProperty(propertyExpression);
_javaScriptTokens.Add(p.Name, (string) p.GetValue(null, null));
}
public void RegisterJavaScriptTokens()
{
AddJavaScriptToken(() => Tokens.TOKEN_ONE);
AddJavaScriptToken(() => Tokens.TOKEN_TWO);
}
Here is a function that will get you the names of all static properties in a given type.
public static IEnumerable<string> GetStaticPropertyNames(Type t) {
foreach ( var prop in t.GetProperties(BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic) ) {
yield return prop.Name;
}
}
If you want to build up the map of all property names to their values you can do the following
public static Dictionary<string,object> GetStaticPropertyBag(Type t) {
var flags = BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic);
var map = new Dictionary<string,object>();
foreach ( var prop in t.GetProperties(flags) ) {
map[prop.Name] = prop.GetValue(null,null);
}
return map;
}
Now you can call it with the following
var bag = GetStaticPropertyBag(typeof(MyResources));
You can accomplish this with reflection. The easiest way to get the property names is to loop over all of them.
foreach(var propInfo in this.GetType().GetProperties()) {
var name = propInfo.Name;
var value = propInfo.GetValue(this, null);
}
See GetProperties() and GetValue() for more specifics.
Well, I'm reluctantly answering my own question because I don't think it's possible to do this for a single static property. Ultimately, I ended up hard-coding the key in the Dictionary using a cut-and-paste of the property name. Here's what I ended up with:
public void RegisterJavaScriptTokens()
{
AddJavaScriptToken(Token.FOOBAR_TITLE, "FOOBAR_TITLE");
}
And here's the rest of the code:
protected Dictionary<String, String> _javaScriptTokens = new Dictionary<String, String>();
public void AddJavaScriptToken(string tokenValue, string propertyName)
{
_javaScriptTokens.Add(propertyName, tokenValue);
}
protected override void OnPreRender(EventArgs e)
{
if (_javaScriptTokens.Count > 0)
{
StringBuilder sb = new StringBuilder();
foreach (KeyValuePair<String, String> kvp in _javaScriptTokens)
{
sb.AppendLine(String.Format("var TOKEN_{0} = unescape('{1}');", kvp.Key, PUtilities.Escape(kvp.Value)));
}
ClientScript.RegisterStartupScript(this.GetType(), "PAGE_TOKENS", sb.ToString(), true);
}
base.OnPreRender(e);
}
I hate having to use cut-and-paste hard-coding to keep the property name and the key in sync...Oh well...
Other answers have already explained how you can get a list of the static properties via Reflection. You said you don’t want all of them, only a subset of them. It seems, therefore, that you need a way to distinguish the properties you want from the ones you don’t want. One way to do this is using custom attributes.
Declare a custom attribute class:
[AttributeUsage(AttributeTargets.Property)]
public class WantThisAttribute : Attribute { }
Add this custom attribute to the properties you want:
public static class MyResources
{
[WantThis]
public static string TOKEN_ONE { get { return "One"; } }
[WantThis]
public static string TOKEN_TWO { get { return "Two"; } }
public static string DontWantThis { get { return "Nope"; } }
}
Iterate over the properties to find the ones you want:
public static Dictionary<string, object> GetStaticPropertyBag(Type t)
{
var flags = BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic;
var map = new Dictionary<string, object>();
foreach (var prop in t.GetProperties(flags))
if (prop.IsDefined(typeof(WantThisAttribute), true))
map[prop.Name] = prop.GetValue(null,null);
return map;
}
I have three classes: SomeThing, SomeOtherThing, and YetAntherThing. All three have an identical member called Properties. In each class, it is a key/value pair such that I can reference obj1.Name, obj1.Value, obj2.Name, obj2.Value, obj3.Name, and obj3.Value. I'd like to pass these three objects into a single method that could iterate through their respective "Properties" collections without having to know at compile time which it was operating on. I envision something like:
SomeThing obj1;
SomeOtherThing obj2;
YetAntherThing obj3;
DoProperties( obj1, obj1.GetType() );
DoProperties( obj2, obj2.GetType() );
DoProperties( obj3, obj3.GetType() );
...
private void DoProperties( object obj, Type objectType )
{
// this is where I get lost. I want to "cast" 'obj' to the type
// held in 'objectType' so that I can do something like:
//
// foreach ( var prop in obj.Properties )
// {
// string name = prop.Name;
// string value = prop.Value;
// }
}
Note: The classes SomeThing, SomeOtherThing, and YetAntherThing are defined externally, I have no control over them or access to their source code, and they are all sealed.
You've got two options; either get each class to implement an interface that exposes the collection, eg:
interface IHasProperties
{
PropertyCollection Properties {get;}
}
Then declare your method, referencing that interface:
private void DoProperties(IHasProperties obj)
{
foreach (var prop in obj.Properties)
{
string name = prop.Name;
string value = prop.Value;
}
}
Or use reflection to look-up the Properties collection at run-time, e.g.:
private void DoProperties(object obj)
{
Type objectType = obj.GetType();
var propertyInfo = objectType.GetProperty("Properties", typeof(PropertyCollection));
PropertyCollection properties = (PropertyCollection)propertyInfo.GetValue(obj, null);
foreach (var prop in properties)
{
// string name = prop.Name;
// string value = prop.Value;
}
}
The interface mentioned by FacticiusVir is the way to go, if you have control over the source of each object. Absent that, there is a third option in .NET 4. dynamic.
Given
class A
{
public Dictionary<string, string> Properties { get; set; }
}
class B
{
public Dictionary<string, string> Properties { get; set; }
}
class C
{
public Dictionary<string, string> Properties { get; set; }
}
You can accept the parameter as type dynamic and your code will compile (and bomb at runtime if it is not valid).
static void DoSomething(dynamic obj)
{
foreach (KeyValuePair<string, string> pair in obj.Properties)
{
string name = pair.Key;
string value = pair.Value;
// do something
}
}
I want to make a C# Dictionary in which the key is the string name of a static property in a class and the value is the value of the property. Given a static property in the class called MyResources.TOKEN_ONE, how can I get the at the name of the property rather than its value? I only care about the end part of the property name (e.g. "TOKEN_ONE").
I've edited this to mention that I don't want to map all property values in the Dictionary, just a small subset of everything that's in the class. So assume that I want to get the name for a single property. Given MyResources.TOKEN_ONE, I want to get back "MyResources.TOKEN_ONE" or just "TOKEN_ONE".
Here's some sample code that shows what I'm trying to do. I need the property name because I'm trying to generate a javascript variable in which I map the property name to the variable name and the property value to the variable value. For example, I want the C# Dictionary to generate lines like the one below:
var TOKEN_ONE = "One";
using System;
using System.Collections.Generic;
namespace MyConsoleApp
{
class Program
{
static void Main(string[] args)
{
Dictionary<String, String> kvp = new Dictionary<String, String>();
// How can I use the name of static property in a class as the key for the dictionary?
// For example, I'd like to do something like the following where 'PropertyNameFromReflection'
// is a mechanism that would return "MyResources.TOKEN_ONE"
kvp.Add(MyResources.TOKEN_ONE.PropertyNameFromReflection, MyResources.TOKEN_ONE);
kvp.Add(MyResources.TOKEN_TWO.PropertyNameFromReflection, MyResources.TOKEN_TWO);
Console.ReadLine();
}
}
public static class MyResources
{
public static string TOKEN_ONE
{
get { return "One"; }
}
public static string TOKEN_TWO
{
get { return "Two"; }
}
}
}
If all you want is just to be able to refer to a single, specific property in one place in the code without having to refer to it by a literal string, then you can use an expression tree. For example, the following code declares a method that turns such an expression tree into a PropertyInfo object:
public static PropertyInfo GetProperty(Expression<Func<string>> expr)
{
var member = expr.Body as MemberExpression;
if (member == null)
throw new InvalidOperationException("Expression is not a member access expression.");
var property = member.Member as PropertyInfo;
if (property == null)
throw new InvalidOperationException("Member in expression is not a property.");
return property;
}
Now you can do something like this:
public void AddJavaScriptToken(Expression<Func<string>> propertyExpression)
{
var p = GetProperty(propertyExpression);
_javaScriptTokens.Add(p.Name, (string) p.GetValue(null, null));
}
public void RegisterJavaScriptTokens()
{
AddJavaScriptToken(() => Tokens.TOKEN_ONE);
AddJavaScriptToken(() => Tokens.TOKEN_TWO);
}
Here is a function that will get you the names of all static properties in a given type.
public static IEnumerable<string> GetStaticPropertyNames(Type t) {
foreach ( var prop in t.GetProperties(BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic) ) {
yield return prop.Name;
}
}
If you want to build up the map of all property names to their values you can do the following
public static Dictionary<string,object> GetStaticPropertyBag(Type t) {
var flags = BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic);
var map = new Dictionary<string,object>();
foreach ( var prop in t.GetProperties(flags) ) {
map[prop.Name] = prop.GetValue(null,null);
}
return map;
}
Now you can call it with the following
var bag = GetStaticPropertyBag(typeof(MyResources));
You can accomplish this with reflection. The easiest way to get the property names is to loop over all of them.
foreach(var propInfo in this.GetType().GetProperties()) {
var name = propInfo.Name;
var value = propInfo.GetValue(this, null);
}
See GetProperties() and GetValue() for more specifics.
Well, I'm reluctantly answering my own question because I don't think it's possible to do this for a single static property. Ultimately, I ended up hard-coding the key in the Dictionary using a cut-and-paste of the property name. Here's what I ended up with:
public void RegisterJavaScriptTokens()
{
AddJavaScriptToken(Token.FOOBAR_TITLE, "FOOBAR_TITLE");
}
And here's the rest of the code:
protected Dictionary<String, String> _javaScriptTokens = new Dictionary<String, String>();
public void AddJavaScriptToken(string tokenValue, string propertyName)
{
_javaScriptTokens.Add(propertyName, tokenValue);
}
protected override void OnPreRender(EventArgs e)
{
if (_javaScriptTokens.Count > 0)
{
StringBuilder sb = new StringBuilder();
foreach (KeyValuePair<String, String> kvp in _javaScriptTokens)
{
sb.AppendLine(String.Format("var TOKEN_{0} = unescape('{1}');", kvp.Key, PUtilities.Escape(kvp.Value)));
}
ClientScript.RegisterStartupScript(this.GetType(), "PAGE_TOKENS", sb.ToString(), true);
}
base.OnPreRender(e);
}
I hate having to use cut-and-paste hard-coding to keep the property name and the key in sync...Oh well...
Other answers have already explained how you can get a list of the static properties via Reflection. You said you don’t want all of them, only a subset of them. It seems, therefore, that you need a way to distinguish the properties you want from the ones you don’t want. One way to do this is using custom attributes.
Declare a custom attribute class:
[AttributeUsage(AttributeTargets.Property)]
public class WantThisAttribute : Attribute { }
Add this custom attribute to the properties you want:
public static class MyResources
{
[WantThis]
public static string TOKEN_ONE { get { return "One"; } }
[WantThis]
public static string TOKEN_TWO { get { return "Two"; } }
public static string DontWantThis { get { return "Nope"; } }
}
Iterate over the properties to find the ones you want:
public static Dictionary<string, object> GetStaticPropertyBag(Type t)
{
var flags = BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic;
var map = new Dictionary<string, object>();
foreach (var prop in t.GetProperties(flags))
if (prop.IsDefined(typeof(WantThisAttribute), true))
map[prop.Name] = prop.GetValue(null,null);
return map;
}
For example I have a simple class like
public class Person{
public int Age {get;set;}
public string Name {get;set;}
}
I need to make a method that takes any class and spits out values of properties set in the object as a string in format "Age:35;Name:John Doe;"
I am looking for a method signature on the lines of
public string SpitNameValuePairs<T>()
or something like it. How can this be done efficiently if using reflection?
Here is a quick implementation.
public static string SplitNameValuePairs(object value)
{
string retVal = string.Empty;
List<string> keyValuePairs = new List<string>();
foreach (var propInfo in value.GetType().GetProperties())
{
keyValuePairs.Add(string.Format("{0}:{1};", propInfo.Name, propInfo.GetValue(value, null).ToString()));
}
retVal = string.Join("", keyValuePairs.ToArray());
return retVal;
}
Then called like this:
var person = new Person();
person.Name = "Hello";
person.Age = 10;
Console.WriteLine(SplitNameValuePairs(person));
That have protection from crashes when property have an indexer defined and also it output only instance properties (no static).
private static string SplitNameValuePairs<T>(T value)
{
StringBuilder sb = new StringBuilder();
foreach (PropertyInfo property in typeof(T).GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic))
{
if (property.GetIndexParameters().Length == 0)
sb.AppendFormat("{0}:{1};", property.Name, property.GetValue(value, null));
}
return sb.ToString();
}