Support 'for XML and for JSON' queries (#75)

* Set isXMl and isJson for 'for xml/json' resultSets

* Change string comparison

* Modify if-else

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/Contracts/DbColumnWrapper.cs

@@ -182,7 +182,12 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution.Contracts
         /// <summary>
         /// Whether or not the column is XML
         /// </summary>
-        public bool IsXml { get; private set; }
+        public bool IsXml { get; set; }
+
+        /// <summary>
+        /// Whether or not the column is JSON
+        /// </summary>
+        public bool IsJson { get; set; }
 
         #endregion
 

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/ResultSet.cs

@@ -24,6 +24,11 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
         // xml is a special case so number of chars to store is usually greater than for other long types
         private const int DefaultMaxXmlCharsToStore = 2097152; // 2 MB - QE default
 
+        // Column names of 'for xml' and 'for json' queries
+        private const string NameOfForXMLColumn = "XML_F52E2B61-18A1-11d1-B105-00805F49916B";
+        private const string NameOfForJSONColumn = "JSON_F52E2B61-18A1-11d1-B105-00805F49916B";
+
+
         #endregion
 
         #region Member Variables
@@ -192,6 +197,8 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
                     currentFileOffset += fileWriter.WriteRow(DataReader);
                 }
             }
+            // Check if resultset is 'for xml/json'. If it is, set isJson/isXml value in column metadata
+            SingleColumnXmlJsonResultSet();
 
             // Mark that result has been read
             hasBeenRead = true;
@@ -225,5 +232,30 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
         }
 
         #endregion
+
+        #region Private Helper Methods
+
+        /// <summary>
+        /// If the result set represented by this class corresponds to a single XML
+        /// column that contains results of "for xml" query, set isXml = true 
+        /// If the result set represented by this class corresponds to a single JSON
+        /// column that contains results of "for json" query, set isJson = true
+        /// </summary>
+        private void SingleColumnXmlJsonResultSet() {
+
+            if (Columns?.Length == 1)
+            {   
+                if (Columns[0].ColumnName.Equals(NameOfForXMLColumn, StringComparison.Ordinal))
+                {
+                    Columns[0].IsXml = true;
+                }
+                else if (Columns[0].ColumnName.Equals(NameOfForJSONColumn, StringComparison.Ordinal))
+                {
+                    Columns[0].IsJson = true;
+                }                
+            }
+        }
+
+        #endregion
     }
 }