(avro) branch main updated: AVRO-4161: [C#] Fix System.Decimal to Avro decimal conversion (#3423)

[mgrigorov]

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mgrigorov pushed a commit to branch main
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The following commit(s) were added to refs/heads/main by this push:
     new 0997c339b3 AVRO-4161: [C#] Fix System.Decimal to Avro decimal 
conversion (#3423)
0997c339b3 is described below

commit 0997c339b3c08ada6442e8bbeb1a402c348de7c4
Author: Robert Yokota <rayok...@gmail.com>
AuthorDate: Fri Jul 11 15:10:27 2025 -0700

    AVRO-4161: [C#] Fix System.Decimal to Avro decimal conversion (#3423)
    
    * AVRO-4161: [C#] Fix System.Decimal to Avro decimal conversion
    
    * Fix test
    
    * Add test for negative high precision value
---
 lang/csharp/src/apache/main/AvroDecimal.cs     |  7 +++++--
 lang/csharp/src/apache/test/AvroDecimalTest.cs | 22 +++++++++++++++++++++-
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/lang/csharp/src/apache/main/AvroDecimal.cs 
b/lang/csharp/src/apache/main/AvroDecimal.cs
index 98de9b1b13..794617c497 100644
--- a/lang/csharp/src/apache/main/AvroDecimal.cs
+++ b/lang/csharp/src/apache/main/AvroDecimal.cs
@@ -53,8 +53,11 @@ namespace Avro
         {
             var bytes = GetBytesFromDecimal(value);
 
-            var unscaledValueBytes = new byte[12];
-            Array.Copy(bytes, unscaledValueBytes, unscaledValueBytes.Length);
+            // Copy the first 12 bytes of the decimal into an array of size 13
+            // so that the last byte is 0, which is required by the
+            // BigInteger constructor to ensure the unscaled value is positive.
+            var unscaledValueBytes = new byte[13];
+            Array.Copy(bytes, unscaledValueBytes, 12);
 
             var unscaledValue = new BigInteger(unscaledValueBytes);
             var scale = bytes[14];
diff --git a/lang/csharp/src/apache/test/AvroDecimalTest.cs 
b/lang/csharp/src/apache/test/AvroDecimalTest.cs
index 4a8654aa8a..f90b11a324 100644
--- a/lang/csharp/src/apache/test/AvroDecimalTest.cs
+++ b/lang/csharp/src/apache/test/AvroDecimalTest.cs
@@ -38,10 +38,30 @@ namespace Avro.test
         {
             var valueString = value.ToString();
 
-            var avroDecimal = new AvroDecimal(value);            
+            var avroDecimal = new AvroDecimal(value);
             var avroDecimalString = avroDecimal.ToString();
 
             Assert.AreEqual(valueString, avroDecimalString);
         }
+
+        [Test]
+        public void TestHighPrecisionAvroDecimalToString()
+        {
+            var value = 4.1748330066797328106875724512m; // High precision 
decimal value
+            var valueString = value.ToString();
+
+            var avroDecimal = new AvroDecimal(value);
+            var avroDecimalString = avroDecimal.ToString();
+
+            Assert.AreEqual(valueString, avroDecimalString);
+
+            value = -4.1748330066797328106875724512m; // High precision 
decimal value
+            valueString = value.ToString();
+
+            avroDecimal = new AvroDecimal(value);
+            avroDecimalString = avroDecimal.ToString();
+
+            Assert.AreEqual(valueString, avroDecimalString);
+        }
     }
 }