Exposing DataFrame.ToJson()

src/csharp/Microsoft.Spark.E2ETest/IpcTests/Sql/DataFrameTests.cs

@@ -489,6 +489,8 @@ public void TestSignaturesV2_3_X()
             _df.Show(10, 10);
             _df.Show(10, 10, true);
 
+            Assert.IsType<DataFrame>(_df.ToJson());
+
             Assert.IsType<DataFrame>(_df.Join(_df));
             Assert.IsType<DataFrame>(_df.Join(_df, "name"));
             Assert.IsType<DataFrame>(_df.Join(_df, new[] { "name" }));

src/csharp/Microsoft.Spark/Sql/DataFrame.cs

@@ -218,6 +218,13 @@ public DataFrameNaFunctions Na() =>
         public DataFrameStatFunctions Stat() =>
             new DataFrameStatFunctions((JvmObjectReference)_jvmObject.Invoke("stat"));
 
+        /// <summary>
+        /// Returns the content of the DataFrame as a DataFrame of JSON strings.
+        /// </summary>
+        /// <returns>DataFrame object with JSON strings.</returns>
+        public DataFrame ToJson() =>
+            WrapAsDataFrame(_jvmObject.Invoke("toJSON"));
+
         /// <summary>
         /// Join with another `DataFrame`.
         /// </summary>