We Keep Coding

Call Method by string value from data base

So I have a cell in my Oracle table, its value will be some System function or some Static Property like DateTime.Now.Year.
at the table cell the type is VARCHAR2 in .Net its string.
How can I produce a Generic Code for each case (Property, static Function) to get the value in the string
string str = "DateTime.Now.Year" // the value comes from DataBase
var valueFromDataBase = str.invoke();

Considering you're storing a type and a property
public class Entity
{
public string TypeName { get; set; }
public string PropertyName { get; set; }
}
new Entity { TypeName = typeof(DateTime).FullName ; PropertyName = nameof(DateTime.Now) }
using reflection you can now reverse the process
public static object? GetPropertyValue(string typeName, string propertyName)
{
var assemblies = AppDomain.CurrentDomain.GetAssemblies();
var types = assemblies.SelectMany(a => a.GetTypes());
var type = types.First(t => t.FullName == typeName);
var property = type
.GetProperties(BindingFlags.Public | BindingFlags.Static)
.First(p => p.Name == propertyName);
return property.GetValue(null);
}
var datetime = GetPropertyValue(entityFromDb.TypeName, entityFromDb.PropertyName);

Getting property description attribute

Existing code (simplified)
I have this function
public static string[] GetFieldNames<T>(IEnumerable<T> items)
where T : class
{
var properties = typeof(T).GetProperties().Where(p => SystemTypes.Contains(p.PropertyType)); // Only get System types
return properties.Select(p => p.Name).ToArray();
}
So if say I have this class
class MyClass {
public string Name { get; set; }
[Description("The value")]
public int Value { get; set; }
}
I can have code like this
List<MyClass> items = ...; // Populate items somehow
string[] fieldNames = GetFieldNames(items); // This returns ["Name", "Value"]
That works fine.
The problem
I need to get the Description (if it exists), so that GetFieldNames(items) returns ["Name", "The value"]
How do I modify the GetFieldNames() function to read the Description attribute if it exists?
(Please note that this function has been simplified, the real function is much more complex, so please avoid changing the logic)

This should work for you:
return properties.Select(p =>
Attribute.IsDefined(p, typeof(DescriptionAttribute)) ?
(Attribute.GetCustomAttribute(p, typeof(DescriptionAttribute)) as DescriptionAttribute).Description:
p.Name
).ToArray();

NOTE: just add using System.Reflection as GetCustomAttribute is an extension method in .Net 4.5
public static Tuple<string,string>[] GetFieldNames<T>(IEnumerable<T> items) where T : class
{
var result =
typeof (T).GetProperties()
.Where(p => SystemTypes.Contains(p.PropertyType) &&p.GetCustomAttribute<DescriptionAttribute>() != null)
.Select(
p =>
new Tuple<string, string>(p.Name,
p.GetCustomAttribute<DescriptionAttribute>().Description));
return result.ToArray();
}
for earlier version of .Net framework we can use this extension method:
public static class Extension
{
public static T GetCustomAttribute<T>(this System.Reflection.MemberInfo mi) where T : Attribute
{
return mi.GetCustomAttributes(typeof (T),true).FirstOrDefault() as T;
}
}

This is a generic function you can make use of, if the fieldName has description tag attribute it return the value otherwise it return null.
public string GetDescription<T>(string fieldName)
{
string result;
FieldInfo fi = typeof(T).GetField(fieldName.ToString());
if (fi != null)
{
try
{
object[] descriptionAttrs = fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
DescriptionAttribute description = (DescriptionAttribute)descriptionAttrs[0];
result = (description.Description);
}
catch
{
result = null;
}
}
else
{
result = null;
}
return result;
}
Example:
class MyClass {
public string Name { get; set; }
[Description("The age description")]
public int Age { get; set; }
}
string ageDescription = GetDescription<MyClass>(nameof(Age));
console.log(ageDescription) // OUTPUT: The age description

I am using Description attribute a lot so I wrote Nuget for this purpose.
With it you could just call:
typeof(TestClass).GetPropertyDescription("PropertyName");
It also allows to take DescriptionAttribute from class, field, enum and method.

use GetCustomAttributes Method
static void attributecheck()
{
var props = typeof(Product).GetProperties();
foreach (var propertyInfo in props)
{
var att = propertyInfo.GetCustomAttributes(typeof(DescriptionAttribute), true);
if (att.Length >0)
{
}
}
}

What is the best way to apply these changes to an object without duplicating code?

I am trying update a number of properties of one object from another and I wind up repeating this same code over and over again (i am showing an example with Name and LastName but i have 15 other properties with similar code).
But its important to Note that its NOT all properties so i can't blindly just copy everything.
public class Person
{
public bool UpdateFrom(Person otherPerson)
{
if (!String.IsNullOrEmpty(otherPerson.Name))
{
if (Name!= otherPerson.Name)
{
change = true;
Name = otherPerson.Name;
}
}
if (!String.IsNullOrEmpty(otherPerson.LastName))
{
if (LastName!= otherPerson.LastName)
{
change = true;
LastName = otherPerson.LastName;
}
}
return change;
}
}
is there a more elegant way to writing this code?

You could use an Expression to define which field you want to access, the code to handle the updates would look like this:-
Person one = new Person {FirstName = "First", LastName = ""};
Person two = new Person {FirstName = "", LastName = "Last"};
Person three = new Person ();
bool changed = false;
changed = SetIfNotNull(three, one, p => p.FirstName) || changed;
changed = SetIfNotNull(three, one, p => p.LastName) || changed;
changed = SetIfNotNull(three, two, p => p.FirstName) || changed;
changed = SetIfNotNull(three, two, p => p.LastName) || changed;
Note that the order in the || expression matters since .NET will short-circuit the evaluation if it can. Or as Ben suggests in the comments below, use changed |= ... as a simpler alternative.
The SetIfNotNull method relies on this other method that does a bit of Expression magic to convert a getter ino a setter.
/// <summary>
/// Convert a lambda expression for a getter into a setter
/// </summary>
public static Action<T, U> GetSetter<T, U>(Expression<Func<T, U>> expression)
{
var memberExpression = (MemberExpression)expression.Body;
var property = (PropertyInfo)memberExpression.Member;
var setMethod = property.GetSetMethod();
var parameterT = Expression.Parameter(typeof(T), "x");
var parameterU = Expression.Parameter(typeof(U), "y");
var newExpression =
Expression.Lambda<Action<T, U>>(
Expression.Call(parameterT, setMethod, parameterU),
parameterT,
parameterU
);
return newExpression.Compile();
}
public static bool SetIfNotNull<T> (T destination, T source,
Expression<Func<T, string>> getter)
{
string value = getter.Compile()(source);
if (!string.IsNullOrEmpty(value))
{
GetSetter(getter)(destination, value);
return true;
}
else
{
return false;
}
}

Using Func and Action delegates you can do it like this:
public class Person
{
public string Name { get; set; }
public string LastName { get; set; }
public bool UpdateFrom(Person otherPerson)
{
bool change = false;
change = Check(otherPerson.Name, p => p.Name, (p, val) => p.Name = val);
change = change ||
Check(otherPerson.LastName, p => p.LastName, (p, val) => p.LastName = val);
return change;
}
public bool Check(string value, Func<Person, string> getMember, Action<Person, string> action)
{
bool result = false;
if (!string.IsNullOrEmpty(value))
{
if (getMember(this) != value)
{
result = true;
action(this, value);
}
}
return result;
}
}

You can use reflecton to do it.. here's an example implementation (need to add extra code to handle arrays etc.)
public class Person
{
public bool UpdateFromOther(Person otherPerson)
{
var properties =
this.GetType()
.GetProperties(
BindingFlags.Instance | BindingFlags.Public | BindingFlags.SetProperty
| BindingFlags.GetProperty);
var changed = properties.Any(prop =>
{
var my = prop.GetValue(this);
var theirs = prop.GetValue(otherPerson);
return my != null ? !my.Equals(theirs) : theirs != null;
});
foreach (var propertyInfo in properties)
{
propertyInfo.SetValue(this, propertyInfo.GetValue(otherPerson));
}
return changed;
}
public string Name { get; set; }
}
[Test]
public void Test()
{
var instance1 = new Person() { Name = "Monkey" };
var instance2 = new Person() { Name = "Magic" };
var instance3 = new Person() { Name = null};
Assert.IsFalse(instance1.UpdateFromOther(instance1), "No changes should be detected");
Assert.IsTrue(instance2.UpdateFromOther(instance1), "Change is detected");
Assert.AreEqual("Monkey",instance2.Name, "Property updated");
Assert.IsTrue(instance3.UpdateFromOther(instance1), "Change is detected");
Assert.AreEqual("Monkey", instance3.Name, "Property updated");
}

This is just my comment typed out, you can refer to the comments to your question about further details about this technique.
Define this class:
[AttributeUsage(AttributeTargets.Property)]
public sealed class CloningAttribute : Attribute
{
}
In your Person class:
[Cloning] // <-- applying the attribute only to desired properties
public int Test { get; set; }
public bool Clone(Person other)
{
bool changed = false;
var properties = typeof(Person).GetProperties();
foreach (var prop in properties.Where(x => x.GetCustomAttributes(typeof(CloningAttribute), true).Length != 0))
{
// get current values
var myValue = prop.GetValue(this, null);
var otherValue = prop.GetValue(other, null);
if (prop.PropertyType == typeof(string))
{
// special treatment for string:
// ignore if null !!or empty!!
if (String.IsNullOrEmpty((string)otherValue))
{
continue;
}
}
else
{
// do you want to copy if the other value is null?
if (otherValue == null)
{
continue;
}
}
// compare and only check 'changed' if they are different
if (!myValue.Equals(otherValue))
{
changed = true;
prop.SetValue(this, otherValue, null);
}
}
return changed;
}

You can create generic rewriting tool with will look on properties with particular attribute:
public class Updater
{
public static bool Update(object thisObj, object otherObj)
{
IEnumerable<PropertyInfo> props = thisObj.GetType().GetProperties().Where(
prop => Attribute.IsDefined(prop, typeof(UpdateElementAttribute)));
bool change = false;
foreach (var prop in props)
{
object value = prop.GetValue(otherObj);
if (value != null && (value is string || string.IsNullOrWhiteSpace((string)value)))
{
if (!prop.GetValue(thisObj).Equals(value))
{
change = true;
prop.SetValue(thisObj, value);
}
}
}
return change;
}
}
And then just use it:
public class Person
{
public bool UpdateFrom(Person otherPerson)
{
return Updater.Update(this, otherPerson);
}
[UpdateElement]
public string Name { get; set; }
[UpdateElement]
public string LastName { get; set; }
}

How can I deserialize an XML snippet to configure an already existing object?

Here's my scenario, I've got the following class, and I want to have the constructor deserialize some elements of the class. I would really rather NOT use a factory method here.
public abstract class AccessLevelAgentBase : IAccessLevelAgent
{
public List<AccessLevel> AccessLevels { get; set; }
[XmlElement]
public string PasswordPrompt { get; set; }
[XmlElement]
public string GetAccessLevelKeystroke { get; set; }
[XmlElement]
public int Doohicky { get; set;}
public AccessLevelAgentBase(XElement agentElement)
{
// Some Mojo Here to take agentElement and serialize
// from the XML below to set the values of PasswordPrompt,
// GetAccessLevelKeystroke, and Doohicky.
}
}
The XML:
<AccessLevelAgent>
<PasswordPrompt> Password ?: </PasswordPrompt>
<PromptCommand>Ctrl+X</PromptCommand>
<Doohicky>50</Doohicky>
</AccessLevelAgent>

simple way...
public AccessLevelAgentBase(XElement agentElement)
{
this.AccessLevels = (string)agentElement.Element("AccessLevels");
this.GetAccessLevelKeystroke = (string)agentElement.Element("GetAccessLevelKeystroke");
this.Doohicky = (int)agentElement.Element("Doohicky");
}
... not so simple way...
public AccessLevelAgentBase(XElement agentElement)
{
var type = this.GetType();
var props = from prop in type.GetProperties()
let attrib = prop.GetCustomAttributes(typeof(XmlElementAttribute), true)
.OfType<XmlElementAttribute>()
.FirstOrDefault()
where attrib != null
let elementName = string.IsNullOrWhiteSpace(attrib.ElementName)
? prop.Name
: attrib.ElementName
let value = agentElement.Element(elementName)
where value != null
select new
{
Property = prop,
Element = value,
};
foreach (var item in props)
{
var propType = item.Property.PropertyType;
if (propType == typeof(string))
item.Property.SetValue(this, (string)item.Element, null);
else if (propType == typeof(int))
item.Property.SetValue(this, (int)item.Element, null);
else
throw new NotSupportedException();
}
}

Getting Nested Object Property Value Using Reflection

I have the following two classes:
public class Address
{
public string AddressLine1 { get; set; }
public string AddressLine2 { get; set; }
public string City { get; set; }
public string State { get; set; }
public string Zip { get; set; }
}
public class Employee
{
public string FirstName { get; set; }
public string MiddleName { get; set; }
public string LastName { get; set; }
public Address EmployeeAddress { get; set; }
}
I have an instance of the employee class as follows:
var emp1Address = new Address();
emp1Address.AddressLine1 = "Microsoft Corporation";
emp1Address.AddressLine2 = "One Microsoft Way";
emp1Address.City = "Redmond";
emp1Address.State = "WA";
emp1Address.Zip = "98052-6399";
var emp1 = new Employee();
emp1.FirstName = "Bill";
emp1.LastName = "Gates";
emp1.EmployeeAddress = emp1Address;
I have a method which gets the property value based on the property name as follows:
public object GetPropertyValue(object obj ,string propertyName)
{
var objType = obj.GetType();
var prop = objType.GetProperty(propertyName);
return prop.GetValue(obj, null);
}
The above method works fine for calls like GetPropertyValue(emp1, "FirstName") but if I try GetPropertyValue(emp1, "Address.AddressLine1") it throws an exception because objType.GetProperty(propertyName); is not able to locate the nested object property value. Is there a way to fix this?

public object GetPropertyValue(object obj, string propertyName)
{
foreach (var prop in propertyName.Split('.').Select(s => obj.GetType().GetProperty(s)))
obj = prop.GetValue(obj, null);
return obj;
}
Thanks, I came here looking for an answer to the same problem. I ended up modifying your original method to support nested properties. This should be more robust than having to do nested method calls which could end up being cumbersome for more than 2 nested levels.

This will work for unlimited number of nested property.
public object GetPropertyValue(object obj, string propertyName)
{
var _propertyNames = propertyName.Split('.');
for (var i = 0; i < _propertyNames.Length; i++)
{
if (obj != null)
{
var _propertyInfo = obj.GetType().GetProperty(_propertyNames[i]);
if (_propertyInfo != null)
obj = _propertyInfo.GetValue(obj);
else
obj = null;
}
}
return obj;
}
Usage:
GetPropertyValue(_employee, "Firstname");
GetPropertyValue(_employee, "Address.State");
GetPropertyValue(_employee, "Address.Country.Name");

var address = GetPropertyValue(GetPropertyValue(emp1, "Address"), "AddressLine1");
Object Employee doesn't have a single property named "Address.AddressLine1", it has a property named "Address", which itself has a property named "AddressLine1".

I use this method to get the values from properties (unlimited number of nested property) as below:
"Property"
"Address.Street"
"Address.Country.Name"
public static object GetPropertyValue(object src, string propName)
{
if (src == null) throw new ArgumentException("Value cannot be null.", "src");
if (propName == null) throw new ArgumentException("Value cannot be null.", "propName");
if(propName.Contains("."))//complex type nested
{
var temp = propName.Split(new char[] { '.' }, 2);
return GetPropertyValue(GetPropertyValue(src, temp[0]), temp[1]);
}
else
{
var prop = src.GetType().GetProperty(propName);
return prop != null ? prop.GetValue(src, null) : null;
}
}
Here the Fiddle: https://dotnetfiddle.net/PvKRH0

Yet another variation to throw out there. Short & sweet, supports arbitrarily deep properties, handles null values and invalid properties:
public static object GetPropertyVal(this object obj, string name) {
if (obj == null)
return null;
var parts = name.Split(new[] { '.' }, 2);
var prop = obj.GetType().GetProperty(parts[0]);
if (prop == null)
throw new ArgumentException($"{parts[0]} is not a property of {obj.GetType().FullName}.");
var val = prop.GetValue(obj);
return (parts.Length == 1) ? val : val.GetPropertyVal(parts[1]);
}

Get Nest properties e.g., Developer.Project.Name
private static System.Reflection.PropertyInfo GetProperty(object t, string PropertName)
{
if (t.GetType().GetProperties().Count(p => p.Name == PropertName.Split('.')[0]) == 0)
throw new ArgumentNullException(string.Format("Property {0}, is not exists in object {1}", PropertName, t.ToString()));
if (PropertName.Split('.').Length == 1)
return t.GetType().GetProperty(PropertName);
else
return GetProperty(t.GetType().GetProperty(PropertName.Split('.')[0]).GetValue(t, null), PropertName.Split('.')[1]);
}

I made an extension method on type for this propose:
public static class TypeExtensions
{
public static PropertyInfo GetSubProperty(this Type type, string treeProperty, object givenValue)
{
var properties = treeProperty.Split('.');
var value = givenValue;
foreach (var property in properties.Take(properties.Length - 1))
{
value = value.GetType().GetProperty(property).GetValue(value);
if (value == null)
{
return null;
}
}
return value.GetType().GetProperty(properties[properties.Length - 1]);
}
public static object GetSubPropertyValue(this Type type, string treeProperty, object givenValue)
{
var properties = treeProperty.Split('.');
return properties.Aggregate(givenValue, (current, property) => current.GetType().GetProperty(property).GetValue(current));
}
}

A Modified version of above to get the multilevel nested properties
private static System.Reflection.PropertyInfo GetProperty(object t, string PropertName, out object Value)
{
Value = "";
var v = t.GetType().GetProperties();
if (t.GetType().GetProperties().Count(p => p.Name == PropertName.Split('.')[0]) == 0)
//throw new ArgumentNullException(string.Format("Property {0}, is not exists in object {1}", PropertName, t.ToString()));
return null;
if (PropertName.Split('.').Length == 1)
{
var Value1 = t.GetType().GetProperty(PropertName).GetValue(t, null);
Value = Value1;//.ToString();
return t.GetType().GetProperty(PropertName);
}
else
{
//return GetProperty(t.GetType().GetProperty(PropertName.Split('.')[0]).GetValue(t, null), PropertName.Split('.')[1], out Value);
return GetProperty(t.GetType().GetProperty(PropertName.Split('.')[0]).GetValue(t, null), PropertName.Substring(PropertName.IndexOf('.') + 1, PropertName.Length - PropertName.IndexOf('.') - 1), out Value);
}
}

This will work for level 1 and level 2 object properties e.g. Firstname and Address.AddressLine1
public object GetPropertyValue(object obj, string propertyName)
{
object targetObject = obj;
string targetPropertyName = propertyName;
if (propertyName.Contains('.'))
{
string[] split = propertyName.Split('.');
targetObject = obj.GetType().GetProperty(split[0]).GetValue(obj, null);
targetPropertyName = split[1];
}
return targetObject.GetType().GetProperty(targetPropertyName).GetValue(targetObject, null);
}

I have a problem with struct type in static class, So I must use this method GetNestedType, this is example code if you know property name, If you want to getAll you can use GetNestedTypes
ExpandoObject in this example just use for dynamic add property and value
private void ExtractValuesFromAppconstants(string keyName)
{
Type type = typeof(YourClass);
var examination = type.GetNestedType(keyName);
if (examination != null)
{
var innerTypes = examination.GetNestedTypes();
foreach (var innerType in innerTypes)
{
Console.Writeline($"{innerType.Name}")
}
}
}

Recursive method, in one line...
object GetPropertyValue(object obj, string propertyName)
{
return propertyName.Contains(".") ? GetPropertyValue(obj.GetType().GetProperty(propertyName.Split(".").First()).GetValue(obj), string.Join(".", propertyName.Split(".").Skip(1))) : obj != null ? obj.GetType().GetProperty(propertyName).GetValue(obj) : null;
}

I found that the code posted by DevT almost did the trick but failed when there are collections involved e.g. Applicant.Addresses[0].FirstLine, so I added some code to fix this. I am sure others can improve upon in.
public static object GetPropertyValue(object src, string propName)
{
if (src == null) throw new ArgumentException("Value cannot be null.", "src");
if (propName == null) throw new ArgumentException("Value cannot be null.", "propName");
if (propName.Contains("."))//complex type nested
{
var temp = propName.Split(new char[] { '.' }, 2);
return GetPropertyValue(GetPropertyValue(src, temp[0]), temp[1]);
}
else
{
if (propName.Contains("["))
{
int iterator_start = propName.IndexOf('[');
int iterator_end = propName.IndexOf(']');
string iterator_value = propName.Substring(iterator_start + 1, iterator_end - iterator_start - 1);
string string_to_remove = "[" + iterator_value + "]";
int iterator_number = Convert.ToInt32(iterator_value);
propName = propName.Replace(string_to_remove, "");
var prop2 = src.GetType().GetProperty(propName, BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance);
Type type = prop2.PropertyType;
if (type.IsGenericType && type.GetGenericTypeDefinition()
== typeof(List<>))
{
System.Collections.IList oTheList = (System.Collections.IList)prop2.GetValue(src, null);
return oTheList[iterator_number];
}
}
var prop = src.GetType().GetProperty(propName, BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance);
return prop != null ? prop.GetValue(src, null) : null;
}
}