Add default header name generation for empty CSV headers (#40)

Empty or whitespace-only CSV headers are now automatically assigned default names (e.g., Column0, Column1) instead of causing errors, matching LumenWorks CsvReader behavior and fixing SQL bulk insert issues. Introduced CsvReaderOptions.DefaultHeaderName to allow customization of the generated header prefix. Added comprehensive tests for empty, whitespace, and custom header scenarios. Updated version numbers and changelog.

Author: potatoqualitee

dbatools.library.psd1

@@ -7,7 +7,7 @@
 #
 @{
     # Version number of this module.
-    ModuleVersion          = '2025.12.26'
+    ModuleVersion          = '2025.12.28'
 
     # ID used to uniquely identify this module
     GUID                   = '00b61a37-6c36-40d8-8865-ac0180288c84'

project/Dataplat.Dbatools.Csv/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- **Empty header name generation** - Empty or whitespace-only CSV headers are now automatically assigned default names (e.g., `Column0`, `Column1`) instead of throwing errors. This matches LumenWorks CsvReader behavior and fixes SQL bulk insert failures when CSV files have missing header names.
+- **`DefaultHeaderName` option** - New `CsvReaderOptions.DefaultHeaderName` property allows customizing the prefix for generated header names (default is `"Column"`).
+
 ## [1.1.10] - 2025-12-26
 
 ### Added

project/Dataplat.Dbatools.Csv/Dataplat.Dbatools.Csv.csproj

@@ -7,7 +7,7 @@
 
     <!-- NuGet Package Metadata -->
     <PackageId>Dataplat.Dbatools.Csv</PackageId>
-    <Version>1.1.10</Version>
+    <Version>1.1.15</Version>
     <Authors>Chrissy LeMaire</Authors>
     <Company>Dataplat</Company>
     <Product>Dataplat.Dbatools.Csv</Product>

project/dbatools.Tests/Csv/CsvDataReaderTest.cs

@@ -682,6 +682,143 @@ public void TestDuplicateHeaders_UseFirstOccurrence()
 
         #endregion
 
+        #region Empty Header Tests
+
+        [TestMethod]
+        public void TestEmptyHeader_GeneratesDefaultName()
+        {
+            // LumenWorks compatibility: empty headers become Column#
+            // Reproduces the issue from dbatools where Import-DbaCsv failed
+            // with empty headers causing SQL errors
+            string csv = ",ValidHeader\nValue1,Value2";
+
+            using (var reader = CreateReaderFromString(csv))
+            {
+                Assert.AreEqual(2, reader.FieldCount);
+                Assert.AreEqual("Column0", reader.GetName(0));  // Empty header -> Column0
+                Assert.AreEqual("ValidHeader", reader.GetName(1));
+
+                Assert.IsTrue(reader.Read());
+                Assert.AreEqual("Value1", reader.GetString(0));
+                Assert.AreEqual("Value2", reader.GetString(1));
+            }
+        }
+
+        [TestMethod]
+        public void TestMultipleEmptyHeaders_GeneratesUniqueNames()
+        {
+            // Multiple empty headers should each get a unique name based on their index
+            string csv = ",,ValidHeader,\nA,B,C,D";
+
+            using (var reader = CreateReaderFromString(csv))
+            {
+                Assert.AreEqual(4, reader.FieldCount);
+                Assert.AreEqual("Column0", reader.GetName(0));
+                Assert.AreEqual("Column1", reader.GetName(1));
+                Assert.AreEqual("ValidHeader", reader.GetName(2));
+                Assert.AreEqual("Column3", reader.GetName(3));
+
+                Assert.IsTrue(reader.Read());
+                Assert.AreEqual("A", reader.GetString(0));
+                Assert.AreEqual("B", reader.GetString(1));
+                Assert.AreEqual("C", reader.GetString(2));
+                Assert.AreEqual("D", reader.GetString(3));
+            }
+        }
+
+        [TestMethod]
+        public void TestWhitespaceOnlyHeader_GeneratesDefaultName()
+        {
+            // Whitespace-only headers should also be treated as empty
+            string csv = "   ,ValidHeader\nValue1,Value2";
+
+            using (var reader = CreateReaderFromString(csv))
+            {
+                Assert.AreEqual(2, reader.FieldCount);
+                Assert.AreEqual("Column0", reader.GetName(0));  // Whitespace -> Column0
+                Assert.AreEqual("ValidHeader", reader.GetName(1));
+            }
+        }
+
+        [TestMethod]
+        public void TestCustomDefaultHeaderName()
+        {
+            // Users can customize the default header name prefix
+            string csv = ",ValidHeader\nValue1,Value2";
+            var options = new CsvReaderOptions { DefaultHeaderName = "Field" };
+
+            using (var reader = CreateReaderFromString(csv, options))
+            {
+                Assert.AreEqual(2, reader.FieldCount);
+                Assert.AreEqual("Field0", reader.GetName(0));  // Custom prefix
+                Assert.AreEqual("ValidHeader", reader.GetName(1));
+            }
+        }
+
+        [TestMethod]
+        public void TestEmptyHeaderWithTrimming()
+        {
+            // When trimming is enabled, whitespace headers should still become Column#
+            string csv = "  ,  ValidHeader  \nValue1,Value2";
+            var options = new CsvReaderOptions { TrimmingOptions = ValueTrimmingOptions.All };
+
+            using (var reader = CreateReaderFromString(csv, options))
+            {
+                Assert.AreEqual(2, reader.FieldCount);
+                Assert.AreEqual("Column0", reader.GetName(0));  // Trimmed empty -> Column0
+                Assert.AreEqual("ValidHeader", reader.GetName(1));  // Trimmed
+            }
+        }
+
+        [TestMethod]
+        public void TestEmptyHeaderInMiddle()
+        {
+            // Empty header in the middle of other headers
+            string csv = "First,,Last\nA,B,C";
+
+            using (var reader = CreateReaderFromString(csv))
+            {
+                Assert.AreEqual(3, reader.FieldCount);
+                Assert.AreEqual("First", reader.GetName(0));
+                Assert.AreEqual("Column1", reader.GetName(1));  // Middle empty -> Column1
+                Assert.AreEqual("Last", reader.GetName(2));
+
+                Assert.IsTrue(reader.Read());
+                Assert.AreEqual("A", reader.GetString(0));
+                Assert.AreEqual("B", reader.GetString(1));
+                Assert.AreEqual("C", reader.GetString(2));
+            }
+        }
+
+        [TestMethod]
+        public void TestDefaultHeaderNameValidation_RejectsNull()
+        {
+            Assert.ThrowsException<ArgumentNullException>(() =>
+            {
+                new CsvReaderOptions { DefaultHeaderName = null };
+            });
+        }
+
+        [TestMethod]
+        public void TestDefaultHeaderNameValidation_RejectsEmpty()
+        {
+            Assert.ThrowsException<ArgumentException>(() =>
+            {
+                new CsvReaderOptions { DefaultHeaderName = "" };
+            });
+        }
+
+        [TestMethod]
+        public void TestDefaultHeaderNameValidation_RejectsWhitespace()
+        {
+            Assert.ThrowsException<ArgumentException>(() =>
+            {
+                new CsvReaderOptions { DefaultHeaderName = "   " };
+            });
+        }
+
+        #endregion
+
         #region Culture Support Tests
 
         [TestMethod]

project/dbatools/Csv/Reader/CsvDataReader.cs

@@ -611,15 +611,15 @@ private void ProcessHeaders()
                 var lastOccurrence = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
                 for (int i = 0; i < _fieldsBuffer.Count; i++)
                 {
-                    string name = GetTrimmedHeaderName(_fieldsBuffer[i].Value);
+                    string name = GetTrimmedHeaderName(_fieldsBuffer[i].Value, i);
                     lastOccurrence[name] = i;
                 }
 
                 // Mark non-last occurrences for renaming
                 var tempCounts = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
                 for (int i = 0; i < _fieldsBuffer.Count; i++)
                 {
-                    string name = GetTrimmedHeaderName(_fieldsBuffer[i].Value);
+                    string name = GetTrimmedHeaderName(_fieldsBuffer[i].Value, i);
                     if (lastOccurrence[name] != i)
                     {
                         // This is not the last occurrence, will be renamed
@@ -633,7 +633,7 @@ private void ProcessHeaders()
             // Second pass: create columns
             for (int i = 0; i < _fieldsBuffer.Count; i++)
             {
-                string name = GetTrimmedHeaderName(_fieldsBuffer[i].Value);
+                string name = GetTrimmedHeaderName(_fieldsBuffer[i].Value, i);
 
                 // Check include/exclude filters first
                 if (!ShouldIncludeColumn(name))
@@ -657,13 +657,22 @@ private void ProcessHeaders()
             }
         }
 
-        private string GetTrimmedHeaderName(string name)
+        private string GetTrimmedHeaderName(string name, int fieldIndex)
         {
-            if (_options.TrimmingOptions != ValueTrimmingOptions.None && name != null)
+            string result = name;
+
+            if (_options.TrimmingOptions != ValueTrimmingOptions.None && result != null)
             {
-                return name.Trim();
+                result = result.Trim();
             }
-            return name ?? string.Empty;
+
+            // Generate default header name for empty or whitespace-only headers (LumenWorks compatibility)
+            if (string.IsNullOrEmpty(result) || (result != null && result.Trim().Length == 0))
+            {
+                result = _options.DefaultHeaderName + fieldIndex;
+            }
+
+            return result ?? string.Empty;
         }
 
         private string HandleDuplicateHeader(string name, int fieldIndex)

project/dbatools/Csv/Reader/CsvReaderOptions.cs

@@ -257,6 +257,29 @@ public int MaxParseErrors
         /// </summary>
         public DuplicateHeaderBehavior DuplicateHeaderBehavior { get; set; } = DuplicateHeaderBehavior.ThrowException;
 
+        private string _defaultHeaderName = "Column";
+
+        /// <summary>
+        /// Gets or sets the default header name prefix used for empty or whitespace-only headers.
+        /// The column index will be appended to the specified name (e.g., "Column0", "Column1").
+        /// Default is "Column".
+        /// This matches the behavior of the LumenWorks CSV library.
+        /// </summary>
+        /// <exception cref="ArgumentNullException">Thrown when value is null.</exception>
+        /// <exception cref="ArgumentException">Thrown when value is empty or whitespace-only.</exception>
+        public string DefaultHeaderName
+        {
+            get => _defaultHeaderName;
+            set
+            {
+                if (value == null)
+                    throw new ArgumentNullException(nameof(value), "DefaultHeaderName cannot be null.");
+                if (string.IsNullOrWhiteSpace(value))
+                    throw new ArgumentException("DefaultHeaderName cannot be empty or whitespace-only.", nameof(value));
+                _defaultHeaderName = value;
+            }
+        }
+
         /// <summary>
         /// Gets or sets the culture to use for parsing numbers and dates.
         /// Default is InvariantCulture.
@@ -477,6 +500,7 @@ public CsvReaderOptions Clone()
                 ExcludeColumns = ExcludeColumns != null ? new HashSet<string>(ExcludeColumns) : null,
                 DistinguishEmptyFromNull = DistinguishEmptyFromNull,
                 DuplicateHeaderBehavior = DuplicateHeaderBehavior,
+                DefaultHeaderName = DefaultHeaderName,
                 Culture = Culture,
                 QuoteMode = QuoteMode,
                 MismatchedFieldAction = MismatchedFieldAction,

project/dbatools/dbatools.csproj

@@ -7,8 +7,8 @@
     <Product>dbatools</Product>
     <Description>The dbatools PowerShell Module library</Description>
     <Copyright>Copyright © 2025</Copyright>
-    <AssemblyVersion>0.10.0.79</AssemblyVersion>
-    <FileVersion>0.10.0.79</FileVersion>
+    <AssemblyVersion>0.10.0.80</AssemblyVersion>
+    <FileVersion>0.10.0.80</FileVersion>
     <AssemblyName>dbatools</AssemblyName>
     <SkipFunctionsDepsCopy>false</SkipFunctionsDepsCopy>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>