How can I change this code block to LINQ?

Question

Since the for each loop will iterate so many times, I want to remove the foreach loop from the code. Can I change this to LINQ?

if (frameAndExportRequest.SearchObjectRequest.ObjectSearchFilterDetails
   .Any(field => field.FieldName == "APPROVED_BY_USER_NAME")) 
{
    foreach (var field in frameAndExportRequest.SearchObjectRequest.ObjectSearchFilterDetails) 
    {
        if (field.FieldName == "APPROVED_BY_USER_NAME") 
        {
            field.FieldName = "APPROVED_BY_USER";
        }
    }
}

Answer 1

If there is at most 1 match to be expected then you can use LINQ .FirstOrDefault():

var field = frameAndExportRequest
    .SearchObjectRequest
    .ObjectSearchFilterDetails
    .FirstOrDefault(f => f.FieldName == "APPROVED_BY_USER_NAME");

if (field != null)
    field.FieldName = "APPROVED_BY_USER";

If there could be multiple matches, then you need to use .Where():

var fields = frameAndExportRequest
    .SearchObjectRequest
    .ObjectSearchFilterDetails
    .Where(f => f.FieldName == "APPROVED_BY_USER_NAME")
    .ToList();

fields.ForEach(f => f.FieldName = "APPROVED_BY_USER"); // or use built-in foreach

Or use foreach from the start:

foreach (var field in frameAndExportRequest.SearchObjectRequest.ObjectSearchFilterDetails
    .Where(f => f.FieldName == "APPROVED_BY_USER_NAME"))
{
    field.FieldName = "APPROVED_BY_USER";
}

Note that either you do a foreach, or LINQ does it (or something similar) behind the scenes. There will always be a loop - even in the FirstOrDefault case, only then it could do an early exit, so it could be a bit more efficient than the others if you expect at most one match.