Access a Class (dbcontext) Property Dynamically by Property Name

asp.net-core c# entity-framework-core

Question

I have an OnPost method that is specific to updating a particular object by the name of Status:

public async Task OnPostStatus()
{
            Status ExistingRecord = await _context.Status.FirstOrDefaultAsync(m => m.Id == Status.Id);

            if (ExistingRecord == null)
            {
                _context.Status.Add(Status);

            } else
            {
                ExistingRecord.Description = Status.Description;
                ExistingRecord.Hint = Status.Hint;
                _context.Attach(ExistingRecord).State = EntityState.Modified;
            }
            await _context.SaveChangesAsync();
            StatusMessage = "Saved!";
            await OnGetAsync();

        }

But I actually do this exact same OnPost with 4 other objects that have the exact same properties. So, I want to make it more dynamic by passing in the type of object into the OnPost, like this:

        public async Task OnPost(string objectName)
        {
            var objectName ExistingRecord = await _context.(objectName).FirstOrDefaultAsync(m => m.Id == (objectName).Id);

            if (ExistingRecord == null)
            {
                _context.(objectName).Add((objectName));

            } else
            {
                ExistingRecord.Description = (objectName).Description;
                ExistingRecord.Hint = (objectName).Hint;
                _context.Attach(ExistingRecord).State = EntityState.Modified;
            }
            await _context.SaveChangesAsync();
            StatusMessage = "Saved!";
            await OnGetAsync();

        }

I don't know the specific syntax!

1
1
4/3/2020 7:36:48 PM

Accepted Answer

Since these classes have exactly same fields, you can create a common class as the base class to store the fields.

In my example, there are three tables (tb1, tb2, tb3) and a base class (tbBase),the base class is not related to database:

 public class tbBase
{
    public int Id { get; set; }
    public string Description { get; set; }
    public string Hint { get; set; }
}
public class tb1: tbBase
{

}
public class tb2 : tbBase
{

}
public class tb3 : tbBase
{

}

Then, from the view,take the tbBase class as the parameter and pass it to the post method, as well as a specific table type parameter that needs to be modified.

<form method="post">

    Id:<input id="Id" type="text" name="Id" /><br/>
    Description: <input id="Description" type="text" name="Description" /><br/>
    Hint: <input id="Hint" type="text" name="Hint" /><br/>
    table type:<input id="Text1" type="text" name="type" />
    <input id="Button1" type="submit" value="button" />
</form>

In PageModel, store the key-value pairs of parameter table type and specific type through Dictionary:

        public async Task OnPost(tbBase table, string type)
    {
        Dictionary<string, Type> TableTypeDictionary = new Dictionary<string, Type>()
    {
          { "tb1", typeof(tb1) },
          { "tb2", typeof(tb2) },
          { "tb3", typeof(tb3) }
    };
        dynamic obj = Activator.CreateInstance(TableTypeDictionary[type]);
        for (int i = 0; i < obj.GetType().GetProperties().Length; i++)
        {
            obj.GetType().GetProperties()[i].SetValue(obj, table.GetType().GetProperty(obj.GetType().GetProperties()[i].Name).GetValue(table, null), null);
        }
        var ExistingRecord = _context.Find(TableTypeDictionary[type], obj.Id);
        if (ExistingRecord == null)
        {
            obj.Id = 0;//ID is self growing, no need to customize settings
            _context.Add(obj);
        }
        else
        {
            ExistingRecord.Description = table.Description;
            ExistingRecord.Hint = table.Hint;
            _context.Attach(ExistingRecord).State = EntityState.Modified;
        }
        await _context.SaveChangesAsync();
        StatusMessage = "Saved!";
        await OnGetAsync();

    }
1
4/6/2020 8:43:49 AM


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