Get field from dynamically/programatically named column name with Entity Framework

Question

I'm looking for a method to change column and field names dynamically/programatically;

as:

string iLoadProfileValue = "ColumnName";

string lastCol = DatabaseFunctions.DatabaseClient
.tbl_MeterLoadProfile
.OrderByDescending(a => a.MeterReadDate)
.FirstOrDefault(a => a.MeterID == meterID).iLoadProfileValue;

I'll change iLoadProfileValue's value programatically. And I would like to get that column's value to lastCol variable.

How can it be done?

Thanks a lot.

Done:

Last situation like this: THANKS to thepirat000 and Dismissile

string iLoadProfileValue = "MeterReadDate";
var myEntity = DatabaseFunctions.DatabaseClient.tbl_MeterLoadProfile.OrderByDescending(a => a.MeterReadDate).FirstOrDefault(a => a.MeterID == 6);

if (myEntity != null)
{
    var properties = myEntity.GetType().GetProperty(iLoadProfileValue);
    object value = properties.GetValue(myEntity);
}

Why you use the i prefix on iLoadProfileValue?. Just asking. — thepirat000
– thepirat000, Commented Mar 13, 2014 at 12:27
That's a bad habit :). Starting with i usally means that the variable is an int. — thepirat000
– thepirat000, Commented Mar 13, 2014 at 12:29
Could you look to stackoverflow.com/questions/22383198/… please? — Erçin Dedeoğlu
– Erçin Dedeoğlu, Commented Mar 13, 2014 at 15:52

Dismissile · Accepted Answer · 2014-03-13 12:30:35Z

6

You could use reflection to get a list of properties. Look at the GetProperties() method on System.Type.

http://msdn.microsoft.com/en-us/library/aky14axb(v=vs.110).aspx

public PropertyInfo[] GetProperties()

You could then use LINQ to find a property that maches the one you want:

var myEntity = DatabaseFunctions.DatabaseClient
    .tbl_MeterLoadProfile
    .OrderByDescending(a => a.MeterReadDate)
    .FirstOrDefault(a => a.MeterID == meterID);

if(myEntity != null) {
    var properties = myEntity.GetType().GetProperties();

    // iterate through the list of public properties or query to find the one you want
    // for this example I will just get the first property, and use it to get the value:
    var firstProperty = properties.FirstOrDefault();

    // get the value, it will be an object so you might need to cast it
    object value = firstProperty.GetValue(myEntity);
}

As thepirat000 pointed out in the comments, if you only care about a single property you can call the method GetProperty(string name) instead of GetProperties(). This would probably be more efficient if you only care about one property, and you are not reflecting over all columns in your entity.

edited Mar 13, 2014 at 12:30

answered Mar 13, 2014 at 12:08

Dismissile

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5 Comments

Erçin Dedeoğlu Over a year ago

Thanks for the fast respond. prntscr.com/30ej8f I tried and got like this. How can I dinamically select values with variable?

Dismissile Over a year ago

PropertyInfo has a method called GetValue(object) which takes as its parameter the instance that you want to get the value for. I edited the post to show this. msdn.microsoft.com/en-us/library/hh194385(v=vs.110).aspx

thepirat000 Over a year ago

You probably don't need to get all the properties with GetProperties(), you can just call GetProperty(iLoadProfileValue) to obtain the property.

Dismissile Over a year ago

@thepirat000 Great suggestion. If he wants to get all of the properties in a loop it probably makes sense to use GetProperties, otherwise if you only need a single one then GetProperty makes a lot more sense.

Erçin Dedeoğlu Over a year ago

Could you look to stackoverflow.com/questions/22383198/… please?

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