docs: add XML documentation for DataFrameReader class methods (#49) (#55

)

- Added XML documentation blocks to all public methods in the `DataFrameReader` class.
- Adapted PySpark documentation for .NET, including renaming functions and ensuring terminology aligns with .NET conventions.
- Ensured all method descriptions, parameter explanations, and return types are clearly documented.

src/Spark.Connect.Dotnet/Spark.Connect.Dotnet/Sql/DataFrameReader.cs

@@ -28,12 +28,24 @@ protected internal DataFrameReader()
     }
 #pragma warning restore CS8618
 
+    /// <summary>
+    /// Adds an input option for the underlying data source.
+    /// </summary>
+    /// <param name="key">The key for the option to set.</param>
+    /// <param name="value">The value for the option to set. It can be any primitive type or nullable type.</param>
+    /// <returns>A <see cref="DataFrameReader"/> with the option set.</returns>
     public DataFrameReader Option(string key, string value)
     {
         _options.Add(key, value);
         return this;
     }
 
+
+    /// <summary>
+    /// Adds input options for the underlying data source.
+    /// </summary>
+    /// <param name="options">A list of key-value pairs where each key is a string and each value is a string representing the options to be set.</param>
+    /// <returns>A <see cref="DataFrameReader"/> with the specified options set.</returns>
     public DataFrameReader Options(List<KeyValuePair<string, string>> options)
     {
         foreach (var option in options)
@@ -44,6 +56,11 @@ public DataFrameReader Options(List<KeyValuePair<string, string>> options)
         return this;
     }
 
+    /// <summary>
+    /// Adds input options for the underlying data source.
+    /// </summary>
+    /// <param name="options">A dictionary of string keys and string values representing the options to be set.</param>
+    /// <returns>A <see cref="DataFrameReader"/> with the specified options set.</returns>
     public DataFrameReader Options(Dictionary<string, string> options)
     {
         foreach (var option in options)
@@ -54,12 +71,22 @@ public DataFrameReader Options(Dictionary<string, string> options)
         return this;
     }
 
+    /// <summary>
+    /// Sets the schema of the DataFrame using a string representing the schema's DDL (Data Definition Language).
+    /// </summary>
+    /// <param name="schema">A string representing the schema in DDL format.</param>
+    /// <returns>A <see cref="DataFrameReader"/> with the specified schema.</returns>
     public DataFrameReader Schema(string schema)
     {
         _schema = schema;
         return this;
     }
 
+    /// <summary>
+    /// Sets the schema of the DataFrame using a <see cref="StructType"/> object.
+    /// </summary>
+    /// <param name="schema">A <see cref="StructType"/> object representing the schema.</param>
+    /// <returns>A <see cref="DataFrameReader"/> with the specified schema.</returns>
     public DataFrameReader Schema(StructType schema)
     {
         _schema = schema.FieldsAsDdl();
@@ -71,56 +98,114 @@ public DataFrameReader Schema(AnalyzePlanRequest.Types.Schema schema)
         throw new NotImplementedException();
     }
 
+    /// <summary>
+    /// Loads JSON files from the specified path and returns the results as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="path">The path to the JSON file.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded data.</returns>
     public DataFrame Json(string path)
     {
         return Read(new[] { path }, "json", _options, _schema);
     }
 
+    /// <summary>
+    /// Loads JSON files from the specified paths and returns the results as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="paths">An array of paths to the JSON files.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded data.</returns>
     public DataFrame Json(params string[] paths)
     {
         return Read(paths, "json", _options, _schema);
     }
 
+    /// <summary>
+    /// Loads a CSV file and returns the result as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="path">The path to the CSV file.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded CSV data.</returns>
     public DataFrame Csv(string path)
     {
         return Read(new[] { path }, "csv", _options, _schema);
     }
 
+    /// <summary>
+    /// Loads a CSV file from the specified paths and returns the result as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="paths">An array of paths to the CSV files.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded CSV data.</returns>
     public DataFrame Csv(params string[] paths)
     {
         return Read(paths, "csv", _options, _schema);
     }
 
+    /// <summary>
+    /// Loads ORC files and returns the result as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="path">The path to the ORC file.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded ORC data.</returns>
     public DataFrame Orc(string path)
     {
         return Read(new[] { path }, "orc", _options, _schema);
     }
 
+    /// <summary>
+    /// Loads ORC files from the specified paths and returns the result as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="paths">An array of paths to the ORC files.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded ORC data.</returns>
     public DataFrame Orc(params string[] paths)
     {
         return Read(paths, "orc", _options, _schema);
     }
 
+    /// <summary>
+    /// Loads Parquet files and returns the result as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="path">The path to the Parquet file.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded Parquet data.</returns>
     public DataFrame Parquet(string path)
     {
         return Read(new[] { path }, "parquet", _options, _schema);
     }
 
+    /// <summary>
+    /// Loads Parquet files from the specified paths and returns the result as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="paths">An array of paths to the Parquet files.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded Parquet data.</returns>
     public DataFrame Parquet(params string[] paths)
     {
         return Read(paths, "parquet", _options, _schema);
     }
 
+    /// <summary>
+    /// Loads data from a data source and returns it as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="path">The path to the data source.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded data.</returns>
     public DataFrame Load(string path)
     {
         return Read(new[] { path }, _format, _options, _schema);
     }
 
+    /// <summary>
+    /// Loads data from the specified paths and returns it as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="paths">An array of paths to the data sources.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the loaded data.</returns>
     public DataFrame Load(params string[] paths)
     {
         return Read(paths, _format, _options, _schema);
     }
 
+    /// <summary>
+    /// Reads data from the specified paths and returns it as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="paths">An array of paths to the data sources.</param>
+    /// <param name="format">The format of the data source (e.g., "csv", "json", "orc", "parquet").</param>
+    /// <param name="options">A map of additional options to customize the data source reading behavior.</param>
+    /// <param name="schema">An optional schema for the data. If not provided, schema inference will be performed.</param>
+    /// <returns>A <see cref="DataFrame"/> containing the data read from the specified paths.</returns>
     public DataFrame Read(string[] paths, string format, MapField<string, string> options, string schema)
     {
         var datasource = new Read.Types.DataSource
@@ -153,6 +238,15 @@ public DataFrame Read(string[] paths, string format, MapField<string, string> op
         return new DataFrame(_session, plan.Root, new DataType());
     }
 
+    /// <summary>
+    /// Constructs a <see cref="DataFrame"/> representing the database table accessible via a JDBC URL and connection properties.
+    /// </summary>
+    /// <param name="paths">The JDBC URL(s) for the data source.</param>
+    /// <param name="format">The format of the data source, e.g., "jdbc".</param>
+    /// <param name="options">A map of options to customize the JDBC connection (e.g., connection properties, table name, etc.).</param>
+    /// <param name="schema">An optional schema for the data. If not provided, schema inference will be performed.</param>
+    /// <param name="predicates">A list of predicates for partitioning the data (optional).</param>
+    /// <returns>A <see cref="DataFrame"/> representing the database table.</returns>
     public DataFrame Jdbc(string[] paths, string format, MapField<string, string> options, string schema,
         RepeatedField<string> predicates)
     {
@@ -191,12 +285,22 @@ public DataFrame Jdbc(string[] paths, string format, MapField<string, string> op
         return new DataFrame(_session, plan.Root);
     }
 
+    /// <summary>
+    /// Specifies the input data source format.
+    /// </summary>
+    /// <param name="format">The name of the data source format, e.g., 'json', 'parquet', 'csv', etc.</param>
+    /// <returns>A <see cref="DataFrameReader"/> instance that can be used to read data in the specified format.</returns>
     public DataFrameReader Format(string format)
     {
         _format = format;
         return this;
     }
 
+    /// <summary>
+    /// Returns the specified table as a <see cref="DataFrame"/>.
+    /// </summary>
+    /// <param name="name">The name of the table to load as a DataFrame.</param>
+    /// <returns>A <see cref="DataFrame"/> representing the specified table.</returns>
     public DataFrame Table(string name)
     {
         var plan = new Plan