apacheGH-30717: [C#] Add ToString() methods to Arrow classes (apache#…

…36566)

### What changes are included in this PR?

Implemented the ToString() method on classes ChunkedArray, Field, RecordBatch, Schema and Table. 
I could not find the class DataType mentioned in the issue, perhaps it meant DateType?

Closes apache#30717.
* Closes: apache#30717

Lead-authored-by: Gavin Murrison <2135106+voidstar69@users.noreply.github.com>
Co-authored-by: voidstar69 <voidstar69@gmail.com>
Co-authored-by: Weston Pace <weston.pace@gmail.com>
Signed-off-by: Curt Hagenlocher <curt@hagenlocher.org>

csharp/src/Apache.Arrow/ChunkedArray.cs

@@ -92,6 +92,8 @@ public ChunkedArray Slice(long offset)
  return Slice(offset, Length - offset);
  }
 
+ public override string ToString() => $"{nameof(ChunkedArray)}: Length={Length}, DataType={DataType.Name}";
+
  private static IArrowArray[] Cast(IList<Array> arrays)
  {
  IArrowArray[] arrowArrays = new IArrowArray[arrays.Count];

csharp/src/Apache.Arrow/Field.cs

@@ -61,5 +61,7 @@ private Field(string name, IArrowType dataType, bool nullable, bool allowBlankNa
  DataType = dataType ?? NullType.Default;
  IsNullable = nullable;
  }
+
+ public override string ToString() => $"{nameof(Field)}: Name={Name}, DataType={DataType.Name}, IsNullable={IsNullable}, Metadata count={Metadata?.Count ?? 0}";
  }
 }

csharp/src/Apache.Arrow/RecordBatch.cs

@@ -93,5 +93,7 @@ public RecordBatch Clone(MemoryAllocator allocator = default)
  IEnumerable<IArrowArray> arrays = _arrays.Select(array => ArrowArrayFactory.BuildArray(array.Data.Clone(allocator)));
  return new RecordBatch(Schema, arrays, Length);
  }
+
+ public override string ToString() => $"{nameof(RecordBatch)}: {ColumnCount} columns by {Length} rows";
  }
 }

csharp/src/Apache.Arrow/Schema.cs

@@ -114,5 +114,7 @@ public Schema SetField(int fieldIndex, Field newField)
 
  return new Schema(fields, Metadata);
  }
+
+ public override string ToString() => $"{nameof(Schema)}: Num fields={_fieldsList.Count}, Num metadata={Metadata?.Count ?? 0}";
  }
 }

csharp/src/Apache.Arrow/Table.cs

@@ -107,6 +107,8 @@ public Table SetColumn(int columnIndex, Column column)
  return new Table(newSchema, newColumns);
  }
 
+ public override string ToString() => $"{nameof(Table)}: {ColumnCount} columns by {RowCount} rows";
+
  // TODO: Flatten for Tables with Lists/Structs?
  }
 }

csharp/test/Apache.Arrow.Tests/ArrowStreamWriterTests.cs

@@ -541,6 +541,10 @@ public async Task WriteMultipleDictionaryArraysAsync()
  public void WriteMultipleDictionaryArrays()
  {
  List<RecordBatch> originalRecordBatches = CreateMultipleDictionaryArraysTestData();
+ Assert.Equal("RecordBatch: 10 columns by 3 rows", originalRecordBatches[0].ToString());
+ Assert.Equal("Schema: Num fields=10, Num metadata=0", originalRecordBatches[0].Schema.ToString());
+ Assert.Equal("Field: Name=dictionaryField_int8, DataType=dictionary, IsNullable=False, Metadata count=0",
+ originalRecordBatches[0].Schema.FieldsLookup["dictionaryField_int8"].Single().ToString());
  TestRoundTripRecordBatches(originalRecordBatches);
  }
 

csharp/test/Apache.Arrow.Tests/TableTests.cs

@@ -49,6 +49,8 @@ public void TestTableBasics()
  Table table = MakeTableWithOneColumnOfTwoIntArrays(10);
  Assert.Equal(20, table.RowCount);
  Assert.Equal(1, table.ColumnCount);
+ Assert.Equal("Table: 1 columns by 20 rows", table.ToString());
+ Assert.Equal("ChunkedArray: Length=20, DataType=int32", table.Column(0).Data.ToString());
  }
 
  [Fact]
@@ -61,6 +63,7 @@ public void TestTableFromRecordBatches()
  Table table1 = Table.TableFromRecordBatches(recordBatch1.Schema, recordBatches);
  Assert.Equal(20, table1.RowCount);
  Assert.Equal(27, table1.ColumnCount);
+ Assert.Equal("ChunkedArray: Length=20, DataType=list", table1.Column(0).Data.ToString());
 
  FixedSizeBinaryType type = new FixedSizeBinaryType(17);
  Field newField1 = new Field(type.Name, type, false);
@@ -83,6 +86,9 @@ public void TestTableFromRecordBatches()
  public void TestTableAddRemoveAndSetColumn()
  {
  Table table = MakeTableWithOneColumnOfTwoIntArrays(10);
+ Assert.Equal("Table: 1 columns by 20 rows", table.ToString());
+ Assert.Equal("Field: Name=f0, DataType=int32, IsNullable=True, Metadata count=0", table.Column(0).Field.ToString());
+ Assert.Equal("ChunkedArray: Length=20, DataType=int32", table.Column(0).Data.ToString());
 
  Array nonEqualLengthIntArray = ColumnTests.MakeIntArray(10);
  Field field1 = new Field.Builder().Name("f1").DataType(Int32Type.Default).Build();