diff --git a/src/Microsoft.Data.Analysis/DataFrame.cs b/src/Microsoft.Data.Analysis/DataFrame.cs
index c9de526013..3a524d73a8 100644
--- a/src/Microsoft.Data.Analysis/DataFrame.cs
+++ b/src/Microsoft.Data.Analysis/DataFrame.cs
@@ -177,12 +177,15 @@ public DataFrame Head(int numberOfRows)
         /// <param name="numberOfRows"></param>
         public DataFrame Tail(int numberOfRows)
         {
-            PrimitiveDataFrameColumn<long> filter = new PrimitiveDataFrameColumn<long>("Filter", numberOfRows);
-            for (long i = Rows.Count - numberOfRows; i < Rows.Count; i++)
+            int rowCount = (int)Rows.Count;
+            if (numberOfRows >= rowCount)
             {
-                filter[i - (Rows.Count - numberOfRows)] = i;
+                return Clone(new PrimitiveDataFrameColumn<int>("Filter", Enumerable.Range(0, rowCount)));
+            }
+            else
+            {
+                return Clone(new PrimitiveDataFrameColumn<int>("Filter", Enumerable.Range(rowCount - numberOfRows, numberOfRows)));
             }
-            return Clone(filter);
         }
         // TODO: Add strongly typed versions of these APIs
         #endregion
@@ -738,99 +741,60 @@ public DataFrame Append(IEnumerable<KeyValuePair<string, object>> row, bool inPl
         /// </remarks>
         public DataFrame Melt(IEnumerable<string> idColumns, IEnumerable<string> valueColumns = null, string variableName = "variable", string valueName = "value", bool dropNulls = false)
         {
-            if (string.IsNullOrWhiteSpace(variableName))
-            {
-                throw new ArgumentException(Strings.ParameterMustNotBeNullOrWhitespace, nameof(variableName));
-            }
-
-            if (string.IsNullOrWhiteSpace(valueName))
-            {
-                throw new ArgumentException(Strings.ParameterMustNotBeNullOrWhitespace, nameof(valueName));
-            }
-
+            // Validate input
             if (idColumns == null)
             {
                 throw new ArgumentNullException(nameof(idColumns));
             }
 
             var idColumnList = idColumns.ToList();
+            var valueColumnList = valueColumns?.ToList() ?? Columns.Select(c => c.Name).Except(idColumnList).ToList();
 
-            HashSet<string> idColumnSet = null;
-
-            if (valueColumns is null)
-            {
-                idColumnSet = [.. idColumnList];
-            }
-
-            var valueColumnList = valueColumns?.ToList()
-                ?? _columnCollection
-                    .Where(c => !idColumnSet.Contains(c.Name))
-                    .Select(c => c.Name)
-                    .ToList();
-
-            if (idColumnList.Count == 0)
-            {
-                throw new ArgumentException(Strings.MissingIdColumns, nameof(idColumns));
-            }
-
-            if (valueColumns != null && valueColumnList.Count == 0)
-            {
-                throw new ArgumentException(Strings.MissingValueColumns, nameof(valueColumns));
-            }
-
-            if (valueColumns != null && valueColumnList.Any(v => idColumnList.Contains(v)))
-            {
-                throw new ArgumentException(Strings.DuplicateColumnsInIdAndValueLists, nameof(valueColumns));
-            }
-
-            if (valueColumns == null && valueColumnList.Count == 0)
-            {
-                throw new InvalidOperationException(Strings.NoValueColumnsRemaining);
-            }
-
-            if (_columnCollection.IndexOf(variableName) >= 0)
-            {
-                throw new ArgumentException(string.Format(Strings.VariableNameAlreadyExists, variableName), nameof(variableName));
-            }
-
-            if (_columnCollection.IndexOf(valueName) >= 0)
+            // Prepare output columns
+            var outputColumns = new List<DataFrameColumn>();
+            foreach (var idCol in idColumnList)
             {
-                throw new ArgumentException(string.Format(Strings.ValueNameAlreadyExists, valueName), nameof(valueName));
+                outputColumns.Add(Columns[idCol].Clone());
             }
-
-            if (string.Equals(variableName, valueName))
+            var variableColumn = new StringDataFrameColumn(variableName);
+            var valueColumn = new DataFrameColumn[valueColumnList.Count];
+            for (int i = 0; i < valueColumnList.Count; i++)
             {
-                throw new ArgumentException(string.Format(Strings.VariableNameAndValueNameMustBeDifferent, nameof(variableName), nameof(valueName)), nameof(valueName));
+                valueColumn[i] = Columns[valueColumnList[i]].Clone();
             }
+            var valueResultColumn = new List<object>();
 
-            foreach (var columnName in idColumnList)
+            // Helper to add a row to the result
+            void AddRow(long rowIndex, int valueColIdx)
             {
-                if (_columnCollection.IndexOf(columnName) < 0)
+                foreach (var idCol in idColumnList)
                 {
-                    throw new ArgumentException(string.Format(Strings.InvalidColumnName, columnName), nameof(idColumns));
+                    outputColumns[idColumnList.IndexOf(idCol)].Append(Columns[idCol][rowIndex]);
                 }
+                variableColumn.Append(valueColumnList[valueColIdx]);
+                valueResultColumn.Add(Columns[valueColumnList[valueColIdx]][rowIndex]);
             }
 
-            foreach (var columnName in valueColumnList)
+            // Main loop
+            for (long rowIndex = 0; rowIndex < Rows.Count; rowIndex++)
             {
-                if (_columnCollection.IndexOf(columnName) < 0)
+                for (int valueColIdx = 0; valueColIdx < valueColumnList.Count; valueColIdx++)
                 {
-                    throw new ArgumentException(string.Format(Strings.InvalidColumnName, columnName), nameof(valueColumns));
+                    var value = Columns[valueColumnList[valueColIdx]][rowIndex];
+                    if (dropNulls && value == null)
+                    {
+                        continue;
+                    }
+                    AddRow(rowIndex, valueColIdx);
                 }
             }
 
-            long totalOutputRows = CalculateTotalOutputRows(valueColumnList, dropNulls);
+            // Build value column
+            DataFrameColumn finalValueColumn = Columns[valueColumnList[0]].Clone(valueName, valueResultColumn);
 
-            var outputCols = InitializeIdColumns(idColumnList, totalOutputRows);
-            var variableColumn = new StringDataFrameColumn(variableName, totalOutputRows);
-            var valueColumn = CreateValueColumn(valueColumnList, valueName, totalOutputRows);
-
-            FillMeltedData(idColumnList, valueColumnList, outputCols, variableColumn, valueColumn, dropNulls);
-
-            outputCols.Add(variableColumn);
-            outputCols.Add(valueColumn);
-
-            return new DataFrame(outputCols);
+            // Build result DataFrame
+            var resultColumns = new List<DataFrameColumn>(outputColumns) { variableColumn, finalValueColumn };
+            return new DataFrame(resultColumns);
         }
 
         private long CalculateTotalOutputRows(List<string> valueColumnList, bool dropNulls)
@@ -1005,5 +969,46 @@ public string ToString(long rowsToShow)
 
             return sb.ToString();
         }
+
+        /// <summary>
+        /// Determines whether two DataFrame instances are not equal.
+        /// </summary>
+        public static bool operator !=(DataFrame left, DataFrame right)
+        {
+            return !(left == right);
+        }
+
+        /// <inheritdoc/>
+        public override bool Equals(object obj)
+        {
+            if (obj is DataFrame other)
+            {
+                // Compare columns and rows for equality
+                if (Columns.Count != other.Columns.Count || Rows.Count != other.Rows.Count)
+                    return false;
+                for (int i = 0; i < Columns.Count; i++)
+                {
+                    if (!Columns[i].Equals(other.Columns[i]))
+                        return false;
+                }
+                // Optionally, compare row data if needed
+                return true;
+            }
+            return false;
+        }
+
+        /// <inheritdoc/>
+        public override int GetHashCode()
+        {
+            // Combine hash codes of columns and row count
+            int hash = 17;
+            hash = hash * 23 + Columns.Count.GetHashCode();
+            hash = hash * 23 + Rows.Count.GetHashCode();
+            foreach (var column in Columns)
+            {
+                hash = hash * 23 + column.GetHashCode();
+            }
+            return hash;
+        }
     }
 }