Sqlite: Empty string init and coalescing for various properties

src/Microsoft.Data.Sqlite.Core/SqliteCommand.cs

@@ -102,7 +102,7 @@ public override string CommandText
                 if (value != _commandText)
                 {
                     DisposePreparedStatements();
-                    _commandText = value;
+                    _commandText = value ?? string.Empty;
                 }
             }
         }

src/Microsoft.Data.Sqlite.Core/SqliteConnection.cs

@@ -36,7 +36,7 @@ public partial class SqliteConnection : DbConnection
 
         private HashSet<(string file, string proc)> _extensions;
 
-        private string _connectionString;
+        private string _connectionString = string.Empty;
         private ConnectionState _state;
         private sqlite3 _db;
         private bool _extensionsEnabled;
@@ -84,7 +84,7 @@ public override string ConnectionString
                     throw new InvalidOperationException(Resources.ConnectionStringRequiresClosedConnection);
                 }
 
-                _connectionString = value;
+                _connectionString = value ?? string.Empty;
                 ConnectionOptions = new SqliteConnectionStringBuilder(value);
             }
         }
@@ -164,7 +164,7 @@ public override void Open()
                 return;
             }
 
-            if (ConnectionString == null)
+            if (string.IsNullOrEmpty(ConnectionString))
             {
                 throw new InvalidOperationException(Resources.OpenRequiresSetConnectionString);
             }

src/Microsoft.Data.Sqlite.Core/SqliteParameter.cs

@@ -18,9 +18,11 @@ namespace Microsoft.Data.Sqlite
     /// <seealso href="https://docs.microsoft.com/dotnet/standard/data/sqlite/types">Data Types</seealso>
     public class SqliteParameter : DbParameter
     {
+        private string _parameterName = string.Empty;
         private object _value;
         private int? _size;
         private SqliteType? _sqliteType;
+        private string _sourceColumn = string.Empty;
 
         /// <summary>
         ///     Initializes a new instance of the <see cref="SqliteParameter" /> class.
@@ -122,7 +124,11 @@ public override ParameterDirection Direction
         ///     Gets or sets the name of the parameter.
         /// </summary>
         /// <value>The name of the parameter.</value>
-        public override string ParameterName { get; set; } = string.Empty;
+        public override string ParameterName
+        {
+            get => _parameterName;
+            set => _parameterName = value ?? String.Empty;
+        }
 
         /// <summary>
         ///     Gets or sets the maximum size, in bytes, of the parameter.
@@ -154,7 +160,11 @@ public override int Size
         ///     Gets or sets the source column used for loading the value.
         /// </summary>
         /// <value>The source column used for loading the value.</value>
-        public override string SourceColumn { get; set; } = string.Empty;
+        public override string SourceColumn
+        {
+            get => _sourceColumn;
+            set => _sourceColumn = value ?? string.Empty;
+        }
 
         /// <summary>
         ///     Gets or sets a value indicating whether the source column is nullable.

test/Microsoft.Data.Sqlite.Tests/SqliteCommandTest.cs

@@ -43,6 +43,17 @@ public void CommandText_defaults_to_empty()
             Assert.Empty(command.CommandText);
         }
 
+        [Fact]
+        public void CommandText_coalesces_to_empty()
+        {
+            var command = new SqliteCommand
+            {
+                CommandText = null
+            };
+
+            Assert.Empty(command.CommandText);
+        }
+
         [Fact]
         public void CommandText_throws_when_set_when_open_reader()
         {

test/Microsoft.Data.Sqlite.Tests/SqliteConnectionStringBuilderTest.cs

@@ -33,6 +33,25 @@ public void Ctor_parses_mode()
             Assert.Equal(SqliteOpenMode.Memory, builder.Mode);
         }
 
+        [Fact]
+        public void ConnectionString_defaults_to_empty()
+        {
+            var builder = new SqliteConnectionStringBuilder();
+
+            Assert.Empty(builder.ConnectionString);
+        }
+
+        [Fact]
+        public void ConnectionString_coalesces_to_empty()
+        {
+            var builder = new SqliteConnectionStringBuilder
+            {
+                ConnectionString = null
+            };
+
+            Assert.Empty(builder.ConnectionString);
+        }
+
         [Fact]
         public void Filename_is_alias_for_DataSource()
         {

test/Microsoft.Data.Sqlite.Tests/SqliteConnectionTest.cs

@@ -27,6 +27,25 @@ public void Ctor_sets_connection_string()
             Assert.Equal(connectionString, connection.ConnectionString);
         }
 
+        [Fact]
+        public void ConnectionString_defaults_to_empty()
+        {
+            var connection = new SqliteConnection();
+
+            Assert.Empty(connection.ConnectionString);
+        }
+
+        [Fact]
+        public void ConnectionString_coalesces_to_empty()
+        {
+            var connection = new SqliteConnection
+            {
+                ConnectionString = null
+            };
+
+            Assert.Empty(connection.ConnectionString);
+        }
+
         [Fact]
         public void ConnectionString_setter_throws_when_open()
         {

test/Microsoft.Data.Sqlite.Tests/SqliteParameterTest.cs

@@ -32,6 +32,44 @@ public void Ctor_sets_other_values()
             Assert.Equal("Column", result.SourceColumn);
         }
 
+        [Fact]
+        public void ParameterName_defaults_to_empty()
+        {
+            var parameter = new SqliteParameter();
+
+            Assert.Empty(parameter.ParameterName);
+        }
+
+        [Fact]
+        public void ParameterName_coalesces_to_empty()
+        {
+            var parameter = new SqliteParameter
+            {
+                ParameterName = null
+            };
+
+            Assert.Empty(parameter.ParameterName);
+        }
+
+        [Fact]
+        public void SourceColumn_defaults_to_empty()
+        {
+            var parameter = new SqliteParameter();
+
+            Assert.Empty(parameter.SourceColumn);
+        }
+
+        [Fact]
+        public void SourceColumn_coalesces_to_empty()
+        {
+            var parameter = new SqliteParameter
+            {
+                SourceColumn = null
+            };
+
+            Assert.Empty(parameter.SourceColumn);
+        }
+
         [Fact]
         public void DbType_defaults_to_string()
         {