.Net: Fix single-quote escaping in OBJECT_ID and dynamic SQL string literals (#13900)

In the SQL Server MEVD provider, table/schema/column names embedded
inside SQL string literals (`N'...'`) were not escaping single quotes.
This could produce broken SQL when names contain single quotes.

For example, a table named `it's` would generate:
```sql
IF OBJECT_ID(N'[dbo].[it's]', N'U') IS NULL
```
which is invalid SQL. The fix produces:
```sql
IF OBJECT_ID(N'[dbo].[it''s]', N'U') IS NULL
```

### Changes

Added `AppendTableNameInsideLiteral` and `AppendIdentifierInsideLiteral`
helper methods that escape single quotes by doubling them, and updated
the 5 call sites where identifiers appear inside string literals:

- `OBJECT_ID` in `CreateTable` (ifNotExists check)
- `OBJECT_ID` in full-text index PK lookup
- Dynamic SQL table name, column names, and catalog name for full-text
indexes

### Tests

Added unit tests for `AppendTableNameInsideLiteral`,
`AppendIdentifierInsideLiteral`, and a
`CreateTable_WithSingleQuoteInName` integration test. All 283 tests pass
(unit + conformance).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: roji

dotnet/src/VectorData/SqlServer/SqlServerCommandBuilder.cs

@@ -31,7 +31,7 @@ internal static List<SqlCommand> CreateTable(
         if (ifNotExists)
         {
             sb.Append("IF OBJECT_ID(N'");
-            sb.AppendTableName(schema, tableName);
+            sb.AppendTableNameInsideLiteral(schema, tableName);
             sb.AppendLine("', N'U') IS NULL");
         }
         sb.AppendLine("BEGIN");
@@ -125,22 +125,22 @@ internal static List<SqlCommand> CreateTable(
             // Full-text indexes require a unique index (we use the primary key)
             sb.AppendLine("DECLARE @pkIndexName NVARCHAR(128);");
             sb.Append("SELECT @pkIndexName = name FROM sys.indexes WHERE object_id = OBJECT_ID(N'");
-            sb.AppendTableName(schema, tableName);
+            sb.AppendTableNameInsideLiteral(schema, tableName);
             sb.AppendLine("') AND is_primary_key = 1;");
 
             sb.AppendLine("DECLARE @ftSql NVARCHAR(MAX);");
             sb.Append("SET @ftSql = N'CREATE FULLTEXT INDEX ON ");
-            sb.AppendTableName(schema, tableName).Append(" (");
+            sb.AppendTableNameInsideLiteral(schema, tableName).Append(" (");
             for (int i = 0; i < fullTextProperties.Count; i++)
             {
-                sb.AppendIdentifier(fullTextProperties[i].StorageName);
+                sb.AppendIdentifierInsideLiteral(fullTextProperties[i].StorageName);
                 if (i < fullTextProperties.Count - 1)
                 {
                     sb.Append(',');
                 }
             }
             sb.Append(") KEY INDEX ' + QUOTENAME(@pkIndexName) + N' ON ");
-            sb.AppendIdentifier(catalogName).AppendLine("';");
+            sb.AppendIdentifierInsideLiteral(catalogName).AppendLine("';");
             sb.AppendLine("EXEC sp_executesql @ftSql;");
         }
 
@@ -897,6 +897,30 @@ internal static StringBuilder AppendIdentifier(this StringBuilder sb, string ide
         return sb;
     }
 
+    /// <summary>
+    /// Same as <see cref="AppendTableName"/>, but for use inside a SQL string literal (N'...'),
+    /// where single quotes must be escaped by doubling them.
+    /// </summary>
+    internal static StringBuilder AppendTableNameInsideLiteral(this StringBuilder sb, string? schema, string tableName)
+    {
+        int start = sb.Length;
+        sb.AppendTableName(schema, tableName);
+        sb.Replace("'", "''", start, sb.Length - start);
+        return sb;
+    }
+
+    /// <summary>
+    /// Same as <see cref="AppendIdentifier"/>, but for use inside a SQL string literal (N'...'),
+    /// where single quotes must be escaped by doubling them.
+    /// </summary>
+    internal static StringBuilder AppendIdentifierInsideLiteral(this StringBuilder sb, string identifier)
+    {
+        int start = sb.Length;
+        sb.AppendIdentifier(identifier);
+        sb.Replace("'", "''", start, sb.Length - start);
+        return sb;
+    }
+
     private static StringBuilder AppendIdentifiers(this StringBuilder sb,
         IEnumerable<PropertyModel> properties,
         string? prefix = null,

dotnet/test/VectorData/SqlServer.ConformanceTests/SqlServerCommandBuilderTests.cs

@@ -27,6 +27,36 @@ public void AppendTableName(string? schema, string table, string expectedFullNam
         Assert.Equal(expectedFullName, result.ToString());
     }
 
+    [Theory]
+    [InlineData("schema", "name", "[schema].[name]")]
+    [InlineData(null, "name", "[name]")]
+    [InlineData("schema", "it's", "[schema].[it''s]")]
+    [InlineData("it's", "name", "[it''s].[name]")]
+    [InlineData("it's", "it's", "[it''s].[it''s]")]
+    [InlineData(null, "it's", "[it''s]")]
+    [InlineData("schema", "[brackets]", "[schema].[[brackets]]]")]
+    public void AppendTableNameInsideLiteral(string? schema, string table, string expectedFullName)
+    {
+        StringBuilder result = new();
+
+        SqlServerCommandBuilder.AppendTableNameInsideLiteral(result, schema, table);
+
+        Assert.Equal(expectedFullName, result.ToString());
+    }
+
+    [Theory]
+    [InlineData("name", "[name]")]
+    [InlineData("it's", "[it''s]")]
+    [InlineData("two''quotes", "[two''''quotes]")]
+    public void AppendIdentifierInsideLiteral(string identifier, string expected)
+    {
+        StringBuilder result = new();
+
+        SqlServerCommandBuilder.AppendIdentifierInsideLiteral(result, identifier);
+
+        Assert.Equal(expected, result.ToString());
+    }
+
     [Theory]
     [InlineData("name", "@name_")] // typical name
     [InlineData("na me", "@na_")] // contains a whitespace, an illegal parameter name character
@@ -149,6 +179,34 @@ PRIMARY KEY ([id])
         Assert.Equal(expectedCommand, command.CommandText, ignoreLineEndingDifferences: true);
     }
 
+    [Fact]
+    public void CreateTable_WithSingleQuoteInName()
+    {
+        var model = BuildModel(
+            [
+                new VectorStoreKeyProperty("id", typeof(long)),
+                new VectorStoreDataProperty("name", typeof(string)),
+            ]);
+
+        using SqlConnection connection = CreateConnection();
+
+        var commands = SqlServerCommandBuilder.CreateTable(connection, "it's", "ta'ble", ifNotExists: true, model);
+
+        var command = Assert.Single(commands);
+        Assert.Equal(
+        "IF OBJECT_ID(N'[it''s].[ta''ble]', N'U') IS NULL" + Environment.NewLine +
+        """
+        BEGIN
+        CREATE TABLE [it's].[ta'ble] (
+        [id] BIGINT IDENTITY,
+        [name] NVARCHAR(MAX),
+        PRIMARY KEY ([id])
+        );
+        END;
+        """,
+        command.CommandText, ignoreLineEndingDifferences: true);
+    }
+
     [Fact]
     public void CreateTable_WithDiskAnnIndex()
     {