Improve EndOfStream detection in CsvDataReader

Replaces the EndOfStream property logic to rely on a new _readReturnedFalse flag, which is set when Read() returns false, ensuring more accurate end-of-stream detection. Also simplifies header name generation by using string.IsNullOrWhiteSpace.

Author: potatoqualitee

project/dbatools.Tests/Csv/CsvDataReaderTest.cs

@@ -1123,11 +1123,10 @@ public void TestParseErrorFlag_TrueWhenErrorSkipped()
                 // The parse will fail and the error will be skipped
                 // Depending on how the parser handles this, the row might be skipped
                 // Let's just verify the flag is accessible
-                bool hadError = false;
                 while (reader.Read())
                 {
-                    if (reader.ParseErrorFlag)
-                        hadError = true;
+                    // ParseErrorFlag is accessible during reading
+                    _ = reader.ParseErrorFlag;
                 }
                 // Parse errors were collected
                 Assert.IsTrue(reader.ParseErrors.Count >= 0);

project/dbatools/Csv/Reader/CsvDataReader.cs

@@ -77,6 +77,7 @@ public sealed class CsvDataReader : IDataReader
         // LumenWorks compatibility flags - reset at start of each Read()
         private bool _missingFieldFlag;
         private bool _parseErrorFlag;
+        private bool _readReturnedFalse;  // True after Read() returns false (EndOfStream)
 
         // Buffer for first data row when no header row (needed to create columns during Initialize)
         private string _bufferedFirstLine;
@@ -671,7 +672,7 @@ private string GetTrimmedHeaderName(string name, int fieldIndex)
             }
 
             // Generate default header name for empty or whitespace-only headers (LumenWorks compatibility)
-            if (string.IsNullOrEmpty(result) || (result != null && result.Trim().Length == 0))
+            if (string.IsNullOrWhiteSpace(result))
             {
                 result = _options.DefaultHeaderName + fieldIndex;
             }
@@ -1498,6 +1499,11 @@ public bool Read()
             {
                 ReportProgressIfNeeded();
             }
+            else
+            {
+                // Mark end of stream when Read() returns false
+                _readReturnedFalse = true;
+            }
 
             return result;
         }
@@ -3821,7 +3827,7 @@ private static char NormalizeSmartQuoteChar(char c)
         /// <remarks>
         /// Provides LumenWorks CsvReader compatibility.
         /// </remarks>
-        public bool EndOfStream => _endOfStream && _bufferPosition >= _bufferLength;
+        public bool EndOfStream => _readReturnedFalse;
 
         /// <summary>
         /// Gets whether the current record had missing fields that were padded with nulls.