尝试一下

方法1:

Try this

Method1:

SqlCommand command = new SqlCommand("insert into TableName values
            (@Col1,@Col2)",connection);
command.Parameters.AddWithValue("@Col2",DBNull.Value);

方法2:

Method2:

SqlCommand command = new SqlCommand("insert into TableName values
            (@Col1,@Col2)",connection);
command.Parameters.Add("@Col2",System.Data.SqlDbType.Int).Value=DBNull.Value;

以下是一些方法: ^ ]

Here are some methods: http://***.com/questions/4555935/how-to-assign-null-to-a-sqlparameter[^]