I'm trying to validate an entity coming from an External context has not changed.

public class Employee 
{
    public int Id { get; set; }
    public string Name { get; set; }  
}

I have a method which takes in an entity which has not been loaded from the context.

public bool Validate(Employee employee)
{
    using (var context = new Context())
    {
        return context.Entry(employee).State == EntityState.Modified;
    }
} 

I would like to attach and verify that the attached entity is not modified from whats in the database.

I would prefer not to manually have to iterate of the properties. Is there a way to hack around this?

CodePudding user response：

No need to attach the external entity. You can use the external entity to set values of the database entity and then check the state of the latter:

public bool Validate(Employee externalEmployee)
{
    using var context = new Context(); // C# 8.0

    var dbEntity = context.Where(x => x.Id == externalEmployee.Id).SingleOrDefault();
    if (dbEntity != null)
    {
        context.Entry(dbEntity).CurrentValues.SetValues(externalEmployee);
        return context.Entry(dbEntity).State == EntityState.Modified;
    }
    return false; // Or true, depending on your semantics.
}

CodePudding user response：

You can try:

public static List<string> GetChanges<T>(this T obj, T dbObj)
    {
        List<string> result = new List<string>();
        var type = typeof(T);

        foreach (var prop in type.GetProperties())
        {
            var newValue = prop.GetValue(obj, null);
            var dbValue = prop.GetValue(dbObj, null);

            if(newValue == null && dbValue != null)
            {
                result.Add(prop.Name);
                continue;
            }

            if (newValue != null && dbValue == null)
            {
                result.Add(prop.Name);
                continue;
            }

            if (newValue == null && dbValue == null)
                continue;

            if (!newValue.ToString().Equals(dbValue.ToString()))
                result.Add(prop.Name);
        }

        return result;
    }

if resultList.Count > 0, your object has changes.

In your Validate Method:

public bool Validate(Employee employee)
        {
            using (var context = new Context())
            {
                Employee dbEmployee = context.Employee.Find(employee.Id);

                if(employee.GetChanges(dbEmployee).Count > 0)
                    return true;

                return false;
            }
        }

It's a god workaround =D

Works for me!