补充 开放 IUpdate UpdateColumns 方法功能；

现实更新实体时，只更新指定的列（与 IgnoreColumns 对应）；

FreeSql.Tests/MySql/Curd/MySqlUpdateTest.cs

@@ -84,6 +84,17 @@ namespace FreeSql.Tests.MySql {
 			Assert.Equal("UPDATE `TestEnumUpdateTb` SET `type` = 'sum211' WHERE (`id` = 0)", sql);
 		}
 		[Fact]
+		public void UpdateColumns() {
+			var sql = update.SetSource(new Topic { Id = 1, Title = "newtitle" }).UpdateColumns(a => a.Title).ToSql().Replace("\r\n", "");
+			Assert.Equal("UPDATE `tb_topic` SET `Title` = ?p_0 WHERE (`Id` = 1)", sql);
+
+			sql = g.mysql.Update<TestEnumUpdateTb>().SetSource(new TestEnumUpdateTb { type = TestEnumUpdateTbType.sum211 }).UpdateColumns(a => a.type).ToSql().Replace("\r\n", "");
+			Assert.Equal("UPDATE `TestEnumUpdateTb` SET `type` = ?p_0 WHERE (`id` = 0)", sql);
+
+			sql = g.mysql.Update<TestEnumUpdateTb>().NoneParameter().SetSource(new TestEnumUpdateTb { type = TestEnumUpdateTbType.sum211 }).UpdateColumns(a => a.type).ToSql().Replace("\r\n", "");
+			Assert.Equal("UPDATE `TestEnumUpdateTb` SET `type` = 'sum211' WHERE (`id` = 0)", sql);
+		}
+		[Fact]
 		public void Set() {
 			var sql = update.Where(a => a.Id == 1).Set(a => a.Title, "newtitle").ToSql().Replace("\r\n", "");
 			Assert.Equal("UPDATE `tb_topic` SET `Title` = ?p_0 WHERE (`Id` = 1)", sql);

FreeSql.Tests/Oracle/Curd/OracleUpdateTest.cs

@@ -49,6 +49,11 @@ namespace FreeSql.Tests.Oracle {
 			Assert.Equal("UPDATE \"TB_TOPIC\" SET \"TITLE\" = :p_0 WHERE (\"ID\" = 1)", sql);
 		}
 		[Fact]
+		public void UpdateColumns() {
+			var sql = update.SetSource(new Topic { Id = 1, Title = "newtitle" }).UpdateColumns(a => a.Title).ToSql().Replace("\r\n", "");
+			Assert.Equal("UPDATE \"TB_TOPIC\" SET \"TITLE\" = :p_0 WHERE (\"ID\" = 1)", sql);
+		}
+		[Fact]
 		public void Set() {
 			var sql = update.Where(a => a.Id == 1).Set(a => a.Title, "newtitle").ToSql().Replace("\r\n", "");
 			Assert.Equal("UPDATE \"TB_TOPIC\" SET \"TITLE\" = :p_0 WHERE (\"ID\" = 1)", sql);

FreeSql.Tests/PostgreSQL/Curd/PostgreSQLUpdateTest.cs

@@ -49,6 +49,11 @@ namespace FreeSql.Tests.PostgreSQL {
 			Assert.Equal("UPDATE \"tb_topic\" SET \"title\" = @p_0 WHERE (\"id\" = 1)", sql);
 		}
 		[Fact]
+		public void UpdateColumns() {
+			var sql = update.SetSource(new Topic { Id = 1, Title = "newtitle" }).UpdateColumns(a => a.Title).ToSql().Replace("\r\n", "");
+			Assert.Equal("UPDATE \"tb_topic\" SET \"title\" = @p_0 WHERE (\"id\" = 1)", sql);
+		}
+		[Fact]
 		public void Set() {
 			var sql = update.Where(a => a.Id == 1).Set(a => a.Title, "newtitle").ToSql().Replace("\r\n", "");
 			Assert.Equal("UPDATE \"tb_topic\" SET \"title\" = @p_0 WHERE (\"id\" = 1)", sql);

FreeSql.Tests/SqlServer/Curd/SqlServerUpdateTest.cs

@@ -60,6 +60,11 @@ namespace FreeSql.Tests.SqlServer {
 			Assert.Equal("UPDATE [tb_topic] SET [Title] = @p_0 WHERE ([Id] = 1)", sql);
 		}
 		[Fact]
+		public void UpdateColumns() {
+			var sql = update.SetSource(new Topic { Id = 1, Title = "newtitle" }).UpdateColumns(a => a.Title).ToSql().Replace("\r\n", "");
+			Assert.Equal("UPDATE [tb_topic] SET [Title] = @p_0 WHERE ([Id] = 1)", sql);
+		}
+		[Fact]
 		public void Set() {
 			var sql = update.Where(a => a.Id == 1).Set(a => a.Title, "newtitle").ToSql().Replace("\r\n", "");
 			Assert.Equal("UPDATE [tb_topic] SET [Title] = @p_0 WHERE ([Id] = 1)", sql);

FreeSql.Tests/Sqlite/Curd/SqliteUpdateTest.cs

@@ -50,6 +50,11 @@ namespace FreeSql.Tests.Sqlite {
 			Assert.Equal("UPDATE \"tb_topic\" SET \"Title\" = @p_0 WHERE (\"Id\" = 1)", sql);
 		}
 		[Fact]
+		public void UpdateColumns() {
+			var sql = update.SetSource(new Topic { Id = 1, Title = "newtitle" }).UpdateColumns(a => a.Title).ToSql().Replace("\r\n", "");
+			Assert.Equal("UPDATE \"tb_topic\" SET \"Title\" = @p_0 WHERE (\"Id\" = 1)", sql);
+		}
+		[Fact]
 		public void Set() {
 			var sql = update.Where(a => a.Id == 1).Set(a => a.Title, "newtitle").ToSql().Replace("\r\n", "");
 			Assert.Equal("UPDATE \"tb_topic\" SET \"Title\" = @p_0 WHERE (\"Id\" = 1)", sql);

FreeSql/Interface/Curd/IUpdate.cs

@@ -51,6 +51,19 @@ namespace FreeSql {
 		/// <returns></returns>
 		IUpdate<T1> IgnoreColumns(string[] columns);
 
+		/// <summary>
+		/// 指定的列，UpdateColumns(a => a.Name) | UpdateColumns(a => new{a.Name,a.Time}) | UpdateColumns(a => new[]{"name","time"})
+		/// </summary>
+		/// <param name="columns">lambda选择列</param>
+		/// <returns></returns>
+		IUpdate<T1> UpdateColumns(Expression<Func<T1, object>> columns);
+		/// <summary>
+		/// 指定的列
+		/// </summary>
+		/// <param name="columns"></param>
+		/// <returns></returns>
+		IUpdate<T1> UpdateColumns(string[] columns);
+
 		/// <summary>
 		/// 设置列的新值，Set(a => a.Name, "newvalue")
 		/// </summary>

FreeSql/Internal/CommonProvider/UpdateProvider.cs

@@ -264,11 +264,28 @@ namespace FreeSql.Internal.CommonProvider {
 			foreach (var col in cols) _ignore.Add(col, true);
 			return this;
 		}
+		public IUpdate<T1> UpdateColumns(Expression<Func<T1, object>> columns) {
+			var cols = _commonExpression.ExpressionSelectColumns_MemberAccess_New_NewArrayInit(null, columns?.Body, false, null).ToDictionary(a => a, a => true);
+			_ignore.Clear();
+			foreach (var col in _table.Columns.Values)
+				if (cols.ContainsKey(col.Attribute.Name) == false)
+					_ignore.Add(col.Attribute.Name, true);
+			return this;
+		}
+
 		public IUpdate<T1> IgnoreColumns(string[] columns) {
 			_ignore.Clear();
 			foreach (var col in columns) _ignore.Add(col, true);
 			return this;
 		}
+		public IUpdate<T1> UpdateColumns(string[] columns) {
+			var cols = columns.ToDictionary(a => a);
+			_ignore.Clear();
+			foreach (var col in _table.Columns.Values)
+				if (cols.ContainsKey(col.Attribute.Name) == false)
+					_ignore.Add(col.Attribute.Name, true);
+			return this;
+		}
 
 		public IUpdate<T1> SetSource(T1 source) => this.SetSource(new[] { source });
 		public IUpdate<T1> SetSource(IEnumerable<T1> source) {