Params constructor on DataFrame (dotnet#2800)

* Params constructor on DataFrame

* Delete redundant constructors

Author: Prashanth Govindarajan

src/Microsoft.Data.Analysis/DataFrame.cs

@@ -33,13 +33,14 @@ public partial class DataFrame
     {
         private readonly DataFrameColumnCollection _columnCollection;
         private readonly DataFrameRowCollection _rowCollection;
-        public DataFrame()
+
+        public DataFrame(IEnumerable<DataFrameColumn> columns)
         {
-            _columnCollection = new DataFrameColumnCollection(OnColumnsChanged);
+            _columnCollection = new DataFrameColumnCollection(columns, OnColumnsChanged);
             _rowCollection = new DataFrameRowCollection(this);
         }
 
-        public DataFrame(IList<DataFrameColumn> columns)
+        public DataFrame(params DataFrameColumn[] columns)
         {
             _columnCollection = new DataFrameColumnCollection(columns, OnColumnsChanged);
             _rowCollection = new DataFrameRowCollection(this);

src/Microsoft.Data.Analysis/DataFrameColumnCollection.cs

@@ -21,18 +21,13 @@ public class DataFrameColumnCollection : Collection<DataFrameColumn>
 
         internal long RowCount { get; set; }
 
-        internal DataFrameColumnCollection(Action columnsChanged) : base()
-        {
-            ColumnsChanged = columnsChanged;
-        }
-
-        internal DataFrameColumnCollection(IList<DataFrameColumn> columns, Action columnsChanged) : base()
+        internal DataFrameColumnCollection(IEnumerable<DataFrameColumn> columns, Action columnsChanged) : base()
         {
             columns = columns ?? throw new ArgumentNullException(nameof(columns));
             ColumnsChanged = columnsChanged;
-            for (int i = 0; i < columns.Count; i++)
+            foreach (DataFrameColumn column in columns)
             {
-                Add(columns[i]);
+                Add(column);
             }
         }
 

tests/Microsoft.Data.Analysis.Tests/DataFrameTests.cs

@@ -235,6 +235,12 @@ public void ColumnAndTableCreationTest()
             dataFrame.Columns.RemoveAt(1);
             Assert.Single(dataFrame.Columns);
             Assert.True(ReferenceEquals(intColumn, dataFrame.Columns[0]));
+
+            // Test the params constructor
+            DataFrame dataFrame1 = new DataFrame(intColumn, floatColumn);
+            Assert.Equal(2, dataFrame1.Columns.Count);
+            Assert.Equal(intColumn, dataFrame1.Columns[0]);
+            Assert.Equal(floatColumn, dataFrame1.Columns[1]);
         }
 
         [Fact]