fix(power-query): Handle COM error when regular Excel tables present (#303)

When Power Query commands (View/Update) iterated ListObjects, they failed with COM error 0x800A03EC when regular Excel tables were present because accessing .QueryTable on non-query tables throws. Changes: - PowerQueryCommands.View.cs: Wrap listObj.QueryTable access in try-catch, skip non-query tables - PowerQueryCommands.Update.cs: Wrap listObj.QueryTable access in try-catch, skip non-query tables - Add regression tests for View and Update with manual tables present - Verify ListObjects iteration is robust to mixed table types Regression tests: - View_WorkbookWithManualTable_ReturnsQueryDetails - Update_WorkbookWithManualTable_UpdatesQuerySuccessfully All Power Query integration tests pass (14 tests). Co-authored-by: Stefan Broenner <stefan.broenner@microsoft.comm>

Author: sbroenne

src/ExcelMcp.Core/Commands/PowerQuery/PowerQueryCommands.Update.cs

@@ -146,7 +146,19 @@ public void Update(IExcelBatch batch, string queryName, string mCode, bool refre
  try
  {
  listObj = listObjects.Item(lo);
- queryTable = listObj.QueryTable;
+
+ // NOTE: Accessing QueryTable on a regular Excel table (not from external data)
+ // throws COMException 0x800A03EC. We must catch and skip such tables.
+ try
+ {
+ queryTable = listObj.QueryTable;
+ }
+ catch (System.Runtime.InteropServices.COMException)
+ {
+ // Regular table without QueryTable - skip it
+ continue;
+ }
+
  if (queryTable == null) continue;
 
  wbConn = queryTable.WorkbookConnection;

src/ExcelMcp.Core/Commands/PowerQuery/PowerQueryCommands.View.cs

@@ -149,7 +149,19 @@ public PowerQueryViewResult View(IExcelBatch batch, string queryName)
  try
  {
  listObj = listObjects.Item(lo);
- queryTable = listObj.QueryTable;
+
+ // NOTE: Accessing QueryTable on a regular Excel table (not from external data)
+ // throws COMException 0x800A03EC. We must catch and skip such tables.
+ try
+ {
+ queryTable = listObj.QueryTable;
+ }
+ catch (System.Runtime.InteropServices.COMException)
+ {
+ // Regular table without QueryTable - skip it
+ continue;
+ }
+
  if (queryTable == null) continue;
 
  wbConn = queryTable.WorkbookConnection;

tests/ExcelMcp.Core.Tests/Integration/Commands/PowerQuery/PowerQueryCommandsTests.ManualTable.cs

@@ -111,4 +111,186 @@ public void List_WorkbookWithManualTable_ReturnsOnlyQueries()
  // Query should be connection-only (manual table shouldn't affect this)
  Assert.True(query.IsConnectionOnly);
  }
+
+ /// <summary>
+ /// Regression test: Verifies View() handles workbooks with manually created tables
+ /// Bug: View() was throwing COMException 0x800A03EC when iterating ListObjects
+ /// because manually created tables don't have QueryTable property.
+ /// Fix: View() now catches COMException when accessing ListObject.QueryTable and skips non-query tables.
+ /// </summary>
+ [Fact]
+ public void View_WorkbookWithManualTable_ReturnsQueryDetails()
+ {
+ // Arrange
+ var testFile = _fixture.CreateTestFile();
+
+ var dataModelCommands = new DataModelCommands();
+ var commands = new PowerQueryCommands(dataModelCommands);
+
+ const string queryName = "TestQuery";
+ const string mCode = @"let
+ Source = #table(
+ {""Column1"", ""Column2""},
+ {
+ {""A"", ""B""},
+ {""C"", ""D""}
+ }
+ )
+in
+ Source";
+
+ // Act
+ using var batch = ExcelSession.BeginBatch(testFile);
+
+ // Step 1: Create a manually created table (no Power Query connection)
+ batch.Execute((ctx, ct) =>
+ {
+ dynamic? sheet = null;
+ dynamic? range = null;
+ dynamic? listObjects = null;
+ try
+ {
+ sheet = ctx.Book.Worksheets.Item(1);
+ sheet.Name = "TestSheet";
+
+ // Add some data
+ range = sheet.Range["A1:B3"];
+ range.Value2 = new object[,]
+ {
+ { "Header1", "Header2" },
+ { "Data1", "Data2" },
+ { "Data3", "Data4" }
+ };
+
+ // Create a manual table (ListObject) - NO QueryTable
+ listObjects = sheet.ListObjects;
+ dynamic? listObject = listObjects.Add(
+ 1, // xlSrcRange (manual table from range)
+ range, // Source range
+ Type.Missing, // LinkSource
+ 1, // xlYes (has headers)
+ Type.Missing // Destination
+ );
+ listObject.Name = "ManualTable";
+ ComUtilities.Release(ref listObject!);
+ }
+ finally
+ {
+ ComUtilities.Release(ref listObjects!);
+ ComUtilities.Release(ref range!);
+ ComUtilities.Release(ref sheet!);
+ }
+ });
+
+ // Step 2: Create a Power Query (connection-only)
+ commands.Create(batch, queryName, mCode, PowerQueryLoadMode.ConnectionOnly);
+
+ // Step 3: View the query - THIS WAS THROWING 0x800A03EC before the fix
+ var result = commands.View(batch, queryName);
+
+ // Assert
+ Assert.True(result.Success, $"View failed: {result.ErrorMessage}");
+ Assert.Equal(queryName, result.QueryName);
+ Assert.NotEmpty(result.MCode);
+ Assert.Contains("Source = #table", result.MCode);
+
+ // Verify load destination detected correctly despite manual table presence
+ Assert.True(result.IsConnectionOnly);
+ }
+
+ /// <summary>
+ /// Regression test: Verifies Update() handles workbooks with manually created tables
+ /// Bug: Update() was throwing COMException 0x800A03EC when iterating ListObjects
+ /// because manually created tables don't have QueryTable property.
+ /// Fix: Update() now catches COMException when accessing ListObject.QueryTable and skips non-query tables.
+ /// </summary>
+ [Fact]
+ public void Update_WorkbookWithManualTable_UpdatesQuerySuccessfully()
+ {
+ // Arrange
+ var testFile = _fixture.CreateTestFile();
+
+ var dataModelCommands = new DataModelCommands();
+ var commands = new PowerQueryCommands(dataModelCommands);
+
+ const string queryName = "TestQuery";
+ const string originalMCode = @"let
+ Source = #table(
+ {""Column1"", ""Column2""},
+ {
+ {""A"", ""B""},
+ {""C"", ""D""}
+ }
+ )
+in
+ Source";
+
+ const string updatedMCode = @"let
+ Source = #table(
+ {""NewCol1"", ""NewCol2"", ""NewCol3""},
+ {
+ {1, 2, 3},
+ {4, 5, 6}
+ }
+ )
+in
+ Source";
+
+ // Act
+ using var batch = ExcelSession.BeginBatch(testFile);
+
+ // Step 1: Create a manually created table (no Power Query connection)
+ batch.Execute((ctx, ct) =>
+ {
+ dynamic? sheet = null;
+ dynamic? range = null;
+ dynamic? listObjects = null;
+ try
+ {
+ sheet = ctx.Book.Worksheets.Item(1);
+ sheet.Name = "TestSheet";
+
+ // Add some data
+ range = sheet.Range["A1:B3"];
+ range.Value2 = new object[,]
+ {
+ { "Header1", "Header2" },
+ { "Data1", "Data2" },
+ { "Data3", "Data4" }
+ };
+
+ // Create a manual table (ListObject) - NO QueryTable
+ listObjects = sheet.ListObjects;
+ dynamic? listObject = listObjects.Add(
+ 1, // xlSrcRange (manual table from range)
+ range, // Source range
+ Type.Missing, // LinkSource
+ 1, // xlYes (has headers)
+ Type.Missing // Destination
+ );
+ listObject.Name = "ManualTable";
+ ComUtilities.Release(ref listObject!);
+ }
+ finally
+ {
+ ComUtilities.Release(ref listObjects!);
+ ComUtilities.Release(ref range!);
+ ComUtilities.Release(ref sheet!);
+ }
+ });
+
+ // Step 2: Create a Power Query (connection-only)
+ commands.Create(batch, queryName, originalMCode, PowerQueryLoadMode.ConnectionOnly);
+
+ // Step 3: Update the query - THIS WAS THROWING 0x800A03EC before the fix
+ commands.Update(batch, queryName, updatedMCode);
+
+ // Step 4: Verify the update by viewing
+ var viewResult = commands.View(batch, queryName);
+ Assert.True(viewResult.Success, $"View after update failed: {viewResult.ErrorMessage}");
+ Assert.Contains("NewCol1", viewResult.MCode);
+ Assert.Contains("NewCol2", viewResult.MCode);
+ Assert.Contains("NewCol3", viewResult.MCode);
+ Assert.DoesNotContain("Column1", viewResult.MCode);
+ }
 }