Dynamically select columns in runtime using entity framework

Question

I have an existing function like this

public int sFunc(string sCol , int iId)
{
    string sSqlQuery = \"  select  \" + sCol + \" from TableName where ID = \         


        

Answer 1

Instead of passing the string column name as a parameter, try passing in a lambda expression, like:

sFunc(x => x.FirstColumnName, rowId);
sFunc(x => x.SecondColumnName, rowId);
...

This will in the end give you intellisense for column names, so you avoid possible errors when column name is mistyped.

More about this here: C# Pass Lambda Expression as Method Parameter

However, if you must keep the same method signature, i.e. to support other/legacy code, then you can try this:

public string sFunc(string sCol , int iId)
{
    return TableRepository.Entities.Where(x => x.ID == iId).Select(x => (string) x.GetType().GetProperty(sCol).GetValue(x)});
}

You might need to adjust this a bit, I didn't have a quick way of testing this.

Answer 2

This might help to solve your problem:

public int sFunc(string sCol, int iId)
{
    var _tableRepository = TableRepository.Entities.Where(x => x.ID == iId).Select(e => e).FirstOrDefault();
    if (_tableRepository == null) return 0;

    var _value = _tableRepository.GetType().GetProperties().Where(a => a.Name == sCol).Select(p => p.GetValue(_tableRepository, null)).FirstOrDefault();

    return _value != null ? Convert.ToInt32(_value.ToString()) : 0;
}

This method now work for dynamically input method parameter sCol.

Answer 3

You could use Reflection, something like this (not tested code):

public string sFunc(string sCol , int iId)
{
  var row = TableRepository.Entities.Where(x => x.ID == iId);
  var type = typeof(row);
  var propInfo = type.GetProperty(sCol);

  if (propInfo != null)
  {
    string value = (string)propInfo.GetValue(row);

    return value;
  }

  return null;
}

Answer 4

You can do this:

        var entity = _dbContext.Find(YourEntity, entityKey);
        // Finds column to select or update
        PropertyInfo propertyInfo = entity.GetType().GetProperty("TheColumnVariable");

Answer 5

You have to try with dynamic LINQ. Details are HERE