Clear RFC table rows before applying values

As tables may be re-used between calls of the same SapFunction,
there may still be rows left over from previous calls.
Before applying parameter data to tables, clear the content of the table to avoid duplicate data.

src/SapNwRfc/Internal/Fields/EnumerableField.cs

@@ -27,6 +27,9 @@ public override void Apply(RfcInterop interop, IntPtr dataHandle)
 
             resultCode.ThrowOnError(errorInfo);
 
+            // Clear the table content before adding more - these tables are re-used between calls
+            interop.DeleteAllRows(tableHandle, out errorInfo);
+
             foreach (TItem row in Value)
             {
                 IntPtr lineHandle = interop.AppendNewRow(tableHandle, out errorInfo);

src/SapNwRfc/Internal/Fields/TableField.cs

@@ -26,6 +26,11 @@ public override void Apply(RfcInterop interop, IntPtr dataHandle)
 
             resultCode.ThrowOnError(errorInfo);
 
+            // Clear the table content before adding more - these tables are re-used between calls
+            interop.DeleteAllRows(tableHandle, out errorInfo);
+
+            resultCode.ThrowOnError(errorInfo);
+
             foreach (TItem row in Value)
             {
                 IntPtr lineHandle = interop.AppendNewRow(tableHandle, out errorInfo);

src/SapNwRfc/Internal/Interop/RfcInterop.cs

@@ -321,6 +321,12 @@ public virtual RfcResultCode MoveToFirstRow(IntPtr tableHandle, out RfcErrorInfo
         public virtual IntPtr AppendNewRow(IntPtr tableHandle, out RfcErrorInfo errorInfo)
             => RfcAppendNewRow(tableHandle, out errorInfo);
 
+        [DllImport(SapNwRfcDllName)]
+        private static extern RfcResultCode RfcDeleteAllRows(IntPtr tableHandle, out RfcErrorInfo errorInfo);
+
+        public virtual RfcResultCode DeleteAllRows(IntPtr tableHandle, out RfcErrorInfo errorInfo)
+            => RfcDeleteAllRows(tableHandle, out errorInfo);
+
         #endregion
 
         #region Server

tests/SapNwRfc.Tests/Internal/InputMapperTests.cs

@@ -307,6 +307,7 @@ public void Apply_Array_ShouldMapRowsAndValues()
             InputMapper.Apply(_interopMock.Object, DataHandle, model);
 
             // Assert
+            _interopMock.Verify(x => x.DeleteAllRows(tableHandle, out errorInfo));
             _interopMock.Verify(x => x.AppendNewRow(tableHandle, out errorInfo), Times.Exactly(numberOfRows));
             foreach (ArrayElement element in model.SomeArray)
             {
@@ -363,6 +364,7 @@ public void Apply_Enumerable_ShouldMapRowsAndValues()
             InputMapper.Apply(_interopMock.Object, DataHandle, model);
 
             // Assert
+            _interopMock.Verify(x => x.DeleteAllRows(tableHandle, out errorInfo));
             _interopMock.Verify(x => x.AppendNewRow(tableHandle, out errorInfo), Times.Exactly(numberOfRows));
             foreach (EnumerableElement element in model.SomeEnumerable)
             {