如何在C＃中将System.Guid转换为字符串

Question

I have the following field definition in a class:

   public Nullable<System.Guid> GlobalId { get; set; }

I have another class with the following:

   public string GlobalId { get; set; }

I would like to put the value of from the field with type System.Guid into the string.

I tried to do this here:

        var questionIds = _questionsRepository.GetAll()
            .Where(m => m.Problem != null &&
            m.Problem.SubTopic != null &&
            m.Problem.SubTopic.Topic != null &&
            m.Problem.SubTopic.Topic.SubjectId == 1)
            .Select(m => new QuestionHeader { GlobalId = (string) m.GlobalId })
            .ToList();
        return questionIds;

But it's giving me an error saying:

   Cannot convert type 'System.Guid?' to 'string'

Can someone tell me how I could do this?

Answer 1

You can get the string representation of the GUID by calling ToString() on it.

As your GUID is nullable, check if it's null before calling ToString() :

string myString = guid.HasValue ? guid.Value.ToString() : "default string value";

Answer 2

You don't cast to string. You use ToString() method.

Like this:

GlobalId = m.GlobalId.ToString()

Answer 3

You can convert a Guid with .ToString():

Guid gid = Guid.NewGuid();

string myID = gid.ToString();

Or using

Convert.ToString

Like:

Guid gid = Guid.NewGuid();

string myID = Convert.ToString(gid);

Answer 4

使用Convert.ToString而不是(string)

GlobalId =  Convert.ToString(m.GlobalId)

Answer 5

GlobalId = m.GlobalId.ToString()

Answer 6

Just use ToString() method

Guid? g = null;    
string s = g.ToString();

in case of null it will return String.Empty otherwise you'll get string representation of your Guid

Answer 7

string Id = Guid.NewGuid().ToString();