cannot convert from 'System.Guid?' to 'System.Guid'


In that case, merely use myNullableVariable.Value (if you're sure it has a value), or (myNullableVariable.HasValue)?myNullableVariable.Value:somedefaulthere if you're not.

One can also use GetValueOrDefault() if one doesn't care if the default is a specific value when the nullable really is null.

The last way to do it is this: myNullableVariable.Value ?? defaultvalue.

See, technically a MyType? variable is a Nullable<MyType> under the covers. There are no implicit or explicit casts between the two, so what you need to do is extract the value out of the Nullable manually. The third way i listed is the most succinct (and best?) way to do it, to that would probably be best in most cases.

Use Guid?.Value property to convert 'System.Guid?' to 'System.Guid'. as following example

 Obj GetValue(Guid yourID)
return FetchObject(yourID)
Void main()
Guid? passvalue;
Obj test = GetValue(passvalue.Value);

First intialize the guid variable.

Guid yourGuid= Guid.NewGuid()

then set value in that which you want for eg:

 Guid defaultId = Guid.NewGuid();
 if (customerRow.GuardianState.Length > 2) {
 Guid StateId = record.StateId ?? defaultId;}

cannot convert from 'System.Guid?' to 'System.Guid'

you are trying to save type System.Guid? to a type system.Guid inside your model you can edit System.Guid? to System.Guid by removing the question mark.

or RCIX answer above

Simply use Nullable<T>.HasValue in if statement to check the value for null, then after it you can use Nullable<T>.Value to gets the value of an underlying type.

int? a = null;
  Console.WriteLine($"a has value {a.Value}");
} else {
  Console.WriteLine("No value found in a");


  1. Rafael

    • 2019/8/27

    Because literals (and rvalues in general) cannot be passed by non-const reference (since it would make no sense if the callee could change 

  2. Bellini

    • 2020/10/2

    The following example compiles in Visual Studio 2015 but not in Visual Studio 2017. C++. // C2440j.cpp struct A { explicit A(int) {} A (double) {} }; int main() { const A& a2 = { 1 }; // error C2440: 'initializing': cannot // convert from 'int' to 'const A &' } To correct the error, use direct initialization:

  3. Jeremias

    • 2020/10/24

    Learn about type conversion errors that cause Compiler Error C2440. 'initializing' : cannot convert from 'type1' to 'type2'

  4. Jalen

    • 2018/11/3

    C# 'cannot convert from 'char[]' to 'char*' 0. Caused by: org.openqa.selenium.InvalidSelectorException: 0. Selenium split webelement text and use to click.

  5. Jeremiah

    • 2019/12/18

    error C2440: 'return' : cannot convert from 'const int' to 'int &' this is the code that generated the error (in bold): template <class T>

  6. Chance

    • 2019/2/2

    Argument 'number' cannot convert from TypeA to TypeB. The type of one argument in a method does not match the type that was passed when the class was instantiated

  7. Callen

    • 2018/4/12

    I am getting this, "Cannot convert value of type 'SKScene.Type' to expected argument type 'SKScene'". this is my code for the problem self.scene?

  8. Milo

    • 2017/1/14

    await roleManager.CreateAsync(new IdentityRole("hey")); // ERROR: Argument 1: cannot convert from 'Microsoft.AspNetCore.Identity.IdentityRole' to 'AspNetCore.Identity.Custom.Models.ApplicationRole' About this error, since you have already configured the Identity use custom ApplicationRole model, when register the RoleManager and create new Role, you should use the ApplicationRole model, instead of IdentityRole .

  9. Justin

    • 2018/9/28

    Error: We cannot convert the value null to type Number. mysteriously appeared. ‎05-01-2021 03:59 AM. I'm working in an ERP reporting project and I have 

  10. Miller

    • 2017/7/4

    Questions: I have created the following function: public void DelegatedCall(Action delegatedMethod) And defined the following method public void foo1(String str) { } However, when I try to call DelegateCall with foo1: DelegatedCall(foo1); …I get the following compiler error: Argument 1: cannot convert from 'method group' to 'System.Action

  11. Trevor

    • 2015/4/10

    Cannot convert value '44253' of type Text to type Date. ‎02-16-2021 03:33 AM. Hi Experts,. I am getting an error while converting data type 

  12. Lyle

    • 2021/5/13

    Message détaillé: Type mismatch: cannot convert from int to String Hello i have a problem with the use of talend. Here I have a sql request and I would like to directly implement it in tDBRow or tDBInput with type of request:

  13. Colin

    • 2015/10/17

    Hi guys, I have a question about this error. I have already assign the value: securePassword = (new System.Net.

  14. Raul

    • 2016/7/3

    From the above example when flatmap is not used it will throw the below error, Type mismatch: cannot convert from List<List<Employee>> to List<Employee>. Without flatmap () the code will look like, private List<List<Employee>> getEmployeesWithMatchingSkills(List<Skills> skills) { List<List<Employee>> matchingSkills = map(skill -> getEmployeeSkills(skill.getSkillId())). collect(Collectors.toList()); return matchingSkills; }

  15. Laci

    • 2017/10/30

    E2034 Cannot convert 'type1' to 'type2' (C++) An assignment, initialization, or expression requires the specified type conversion to be performed, but the 

  16. Mohammed

    • 2020/2/24

    However, you cannot convert between the formal and actual types because the types are not closely related. ACTION: Implement an explicit function to convert 

  17. Luka

    • 2015/3/15

    The value that could not be converted. Parameter 2, The name of the type for the conversion. Severity, 16. SQLCODE, -157. SQLSTATE, 53018.

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