c# - SqlCommand 如何处理整数类型的参数？

Question

如果我有这个变量:

int value = 4;

将作为一些 sql 参数传递:

SqlCommand sqlcmd = new SqlCommand();
sqlcmd.Parameters.Add(new SqlParameter("@value", value));

会自动转成字符串处理吗？或者它可能会引起一些麻烦吗？ IE。当我这样做时:

sqlcmd.ExecuteNonQuery();

Answer 1

始终提供正确的类型，尤其是 int 是危险的。

来自 MSDN :

Use caution when you use this overload of the SqlParameter constructor to specify integer parameter values. Because this overload takes a value of type Object, you must convert the integral value to an Object type when the value is zero, as the following C# example demonstrates:

Parameter = new SqlParameter("@pname", (object)0);

If you do not perform this conversion, the compiler assumes that you are trying to call the SqlParameter (string, SqlDbType) constructor overload.

所以如果你想使用字符串参数，把它转换成正确的类型:

sqlcmd.Parameters.Add(new SqlParameter("@value", value.ToString()));

或

sqlcmd.Parameters.AddWithValue("@value", value.ToString());

或(带有类型)

var p = new SqlParameter("@value", typeof(string));
p.Value = value.ToString()
sqlcmd.Parameters.Add(p);