c# – Wackylabs.net

Came across an interesting little snippet of code today.

var max = list.Max(i => i.Value)

1	var max = list.Max(i => i.Value)

This simply returns the maximum value of the “Value” property in the list. However there is a possible problem with this code, depending on the type of Value and the number of elements in the list.

If there are NO elements in the list and Value is NOT nullable (e.g. it is an Integer) then the above will throw an exception.

If there are NO elements in the list and Value IS nullable then it will return NULL.

var max = list.Max(i => i.Value ?? 0)

1	var max = list.Max(i => i.Value ?? 0)

If the list is empty and Value IS nullable then the above will also throw an exception.

var max = list.Max(i => i.Value) ?? 0

1	var max = list.Max(i => i.Value) ?? 0

If the list is empty and Value IS nullable then the above will return 0.

I recently had to convert an Enum back to its original Xml value so I thought I’d share the little method I wrote with you all incase you wondered how to do it yourself.

Method

public static string ConvertToString(Enum e)
{
    // Get the Type of the enum
    Type t = e.GetType();

    // Get the FieldInfo for the member field with the enums name
    FieldInfo info = t.GetField(e.ToString("G"));

    // Check to see if the XmlEnumAttribute is defined on this field
    if (!info.IsDefined(typeof(XmlEnumAttribute), false))
    {
        // If no XmlEnumAttribute then return the string version of the enum.
        return e.ToString("G");
    }

    // Get the XmlEnumAttribute
    object[] o = info.GetCustomAttributes(typeof(XmlEnumAttribute), false);
    XmlEnumAttribute att = (XmlEnumAttribute)o[0];
    return att.Name;
}

public static string ConvertToString(Enum e)

{

// Get the Type of the enum

Type t = e.GetType();

// Get the FieldInfo for the member field with the enums name

FieldInfo info = t.GetField(e.ToString("G"));

// Check to see if the XmlEnumAttribute is defined on this field

if (!info.IsDefined(typeof(XmlEnumAttribute), false))

{

// If no XmlEnumAttribute then return the string version of the enum.

return e.ToString("G");

}

// Get the XmlEnumAttribute

object[] o = info.GetCustomAttributes(typeof(XmlEnumAttribute), false);

XmlEnumAttribute att = (XmlEnumAttribute)o[0];

return att.Name;

}

Example Enum Class

public enum TestEnumClass
{
    FirstValue = 1,
    SecondValue = 2,
    [System.Xml.Serialization.XmlEnum("The Third one")]
    ThirdValue = 3
}

public enum TestEnumClass

{

FirstValue = 1,

SecondValue = 2,

[System.Xml.Serialization.XmlEnum("The Third one")]

ThirdValue = 3

}

Example usage

An Enum of TestEnumClass.FirstValue will then return “FirstValue”, while TestEnumClass.ThirdValue will return “The Third one”.

Hope you find that useful.

Tag: c#

IEnumberable.Max and Nullable types

Getting the XmlEnumAttribute value for an Enum field

Method

Example Enum Class

Example usage