Fix NullReferenceException when GetMethod is null for a property

Author: y1hao

src/BenchmarkDotNet/Running/BenchmarkConverter.cs

@@ -321,7 +321,7 @@ private static (MemberInfo source, object[] values) GetValidValuesForParamsSourc
                     paramsSourceMethod,
                     sourceType));
 
-            var paramsSourceProperty = sourceType.GetAllProperties().FirstOrDefault(property => property.Name == sourceName && property.GetMethod.IsPublic);
+            var paramsSourceProperty = sourceType.GetAllProperties().FirstOrDefault(property => property.Name == sourceName && property.GetMethod?.IsPublic == true);
 
             if (paramsSourceProperty != default)
                 return (paramsSourceProperty, ToArray(

tests/BenchmarkDotNet.Tests/ParamsSourceTests.cs

@@ -31,5 +31,32 @@ public static IEnumerable<object> Values()
             [Benchmark]
             public object FooBar() => O;
         }
+
+        // #2980
+        [Fact]
+        public void WriteOnlyPropertyDoesThrowNullReferenceException()
+        {
+            var exception = Assert.Throws<InvalidBenchmarkDeclarationException>(
+                () => BenchmarkConverter.TypeToBenchmarks(typeof(ClassWithWriteOnlyProperty)));
+
+            Assert.Contains(nameof(ClassWithWriteOnlyProperty.WriteOnlyValues), exception.Message);
+            Assert.Contains("no public, accessible method/property", exception.Message);
+        }
+
+        public class ClassWithWriteOnlyProperty
+        {
+            private int _writeOnlyValue;
+
+            public int WriteOnlyValues
+            {
+                set { _writeOnlyValue = value; }
+            }
+
+            [ParamsSource(nameof(WriteOnlyValues))]
+            public int MyParam { get; set; }
+
+            [Benchmark]
+            public void Run() { }
+        }
     }
 }