String to enum conversion in C#

Question

I have a combo box where I am displaying some entries like:

Equals
Not Equals 
Less Than
Greater Than

Notice that these strings contain spa

Answer 1

As of C# 8 you can do that using switches. In your example I believe the code would be like this.

enum Operation{Equals, Not_Equals, Less_Than, Greater_Than};

public static string OperationString(Operation opString) =>
    opString switch
    {
        Operation.Equals => "Equals",
        Operation.Not_Equals => "Not Equals",
        Operation.Less_Than=> "Less Than",
        Operation.Greater_Than=> "Greater Than",
        _   => throw new ArgumentException(message: "invalid enum value", paramName: nameof(opString )),
    };

See here for the documentation.

Answer 2

I would use a singleton of this enum mapper class that performs much faster than Enum.Parse (which uses reflection and is really slow). You can then use EnumFromString(typeof(YourEnum), "stringValue") to get your enum.

Answer 3

You can use the Parse method:

 Operarion operation = (Operation)Enum.Parse(typeof(Operation), "Not_Equals");

Some examples here

Answer 4

Either create a dedicated mapper using a dictionary (per Mehrdad's answer) or implement a TypeConverter.

Your custom TypeConverter could either replace " " -> "_" (and vice versa) or it could reflect the enumeration and use an attribute for determining the display text of the item.

enum Operation
{
    [DisplayName("Equals")]
    Equals, 

    [DisplayName("Not Equals")]
    Not_Equals, 

    [DisplayName("Less Than")]
    Less_Than, 

    [DisplayName("Greater Than")]
    Greater_Than
};

public class OperationTypeConverter : TypeConverter
{
    private static Dictionary<string, Operation> operationMap;

    static OperationTypeConverter()
    {
        BindingFlags bindingFlags = BindingFlags.Static | BindingFlags.GetField
            | BindingFlags.Public;

        operationMap = enumType.GetFields(bindingFlags).ToDictionary(
            c => GetDisplayName(c)
            );
    }

    private static string GetDisplayName(FieldInfo field, Type enumType)
    {
        DisplayNameAttribute attr = (DisplayNameAttribute)Attribute.GetCustomAttribute(typeof(DisplayNameAttribute));

        return (attr != null) ? attr.DisplayName : field.Name;
    }

    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
    {
        string stringValue = value as string;

        if (stringValue != null)
        {
            Operation operation;
            if (operationMap.TryGetValue(stringValue, out operation))
            {
                return operation;
            }
            else
            {
                throw new ArgumentException("Cannot convert '" + stringValue + "' to Operation");
            }
        }
    }
}

This implementation could be improved in several ways:

• Make it generic
• Implement ConvertTo
• Support FlagsAttribute

Answer 5

Operation enumVal = (Operation)Enum.Parse(typeof(Operation), "Equals")

For "Not Equals", you obv need to replace spaces with underscores in the above statement

EDIT: The following version replaces the spaces with underscores before attempting the parsing:

string someInputText;
var operation = (Operation)Enum.Parse(typeof(Operation), someInputText.Replace(" ", "_"));

Answer 6

Why use another way : convert Enumeration to String?

Just generate the items of your combo box from your Enumeration.