dotnet
diff --git a/‎src/Microsoft.Data.Analysis/DataFrame.IO.cs
Lines changed: 3 additions & 4 deletions b/‎src/Microsoft.Data.Analysis/DataFrame.IO.cs
Lines changed: 3 additions & 4 deletions
diff --git a/‎test/Microsoft.Data.Analysis.Tests/DataFrame.IOTests.cs
Lines changed: 13 additions & 0 deletions b/‎test/Microsoft.Data.Analysis.Tests/DataFrame.IOTests.cs
Lines changed: 13 additions & 0 deletions
@@ -439,14 +439,13 @@ private static DataFrame ReadCsvLinesIntoDataFrame(WrappedStreamReaderOrStringRe
 
                 if (addIndexColumn)
                 {
-                    PrimitiveDataFrameColumn<int> indexColumn = new PrimitiveDataFrameColumn<int>("IndexColumn", columns[0].Length);
-                    for (int i = 0; i < columns[0].Length; i++)
+                    Int64DataFrameColumn indexColumn = new Int64DataFrameColumn("IndexColumn", columns[0].Length);
+                    for (long i = 0; i < columns[0].Length; i++)
                     {
                         indexColumn[i] = i;
                     }
-                    columns.Insert(0, indexColumn);
+                    ret.Columns.Insert(0, indexColumn);
                 }
-
             }
 
             return ret;
 
@@ -622,6 +622,19 @@ public void TestReadCsvWithRepeatColumnNameInHeader()
             Assert.Matches(@"DataFrame already contains a column called Column( \(Parameter 'column'\)|\r\nParameter name: column)", exp.Message);
         }
 
+        [Fact]
+        public void TestLoadCsvWithAddIndexColumn()
+        {
+            var dataFrame = DataFrame.LoadCsvFromString("11\r\n22\r\n33", header: false, addIndexColumn: true);
+
+            Assert.Equal(2, dataFrame.Columns.Count);
+            Assert.Equal("IndexColumn", dataFrame.Columns[0].Name);
+            Assert.Equal(3, dataFrame.Columns[0].Length);
+
+            for (long i = 0; i < dataFrame.Columns[0].Length; i++)
+                Assert.Equal(i, dataFrame.Columns[0][i]);
+        }
+
         [Fact]
         public void TestReadCsvWithExtraColumnInRow()
         {
Original file line number	Diff line number	Diff line change
`@@ -439,14 +439,13 @@ private static DataFrame ReadCsvLinesIntoDataFrame(WrappedStreamReaderOrStringRe`
`439`	`439`
`440`	`440`	`if (addIndexColumn)`
`441`	`441`	`{`
`442`		`- PrimitiveDataFrameColumn<int> indexColumn = new PrimitiveDataFrameColumn<int>("IndexColumn", columns[0].Length);`
`443`		`- for (int i = 0; i < columns[0].Length; i++)`
	`442`	`+ Int64DataFrameColumn indexColumn = new Int64DataFrameColumn("IndexColumn", columns[0].Length);`
	`443`	`+ for (long i = 0; i < columns[0].Length; i++)`
`444`	`444`	`{`
`445`	`445`	`indexColumn[i] = i;`
`446`	`446`	`}`
`447`		`- columns.Insert(0, indexColumn);`
	`447`	`+ ret.Columns.Insert(0, indexColumn);`
`448`	`448`	`}`
`449`		`-`
`450`	`449`	`}`
`451`	`450`
`452`	`451`	`return ret;`