C#调用SQL中的存储过程中有output参数，存储过程执行过程中返回信息

C#调用SQL中的存储过程中有output参数，类型是字符型的时候一定要指定参数的长度。不然获取到的结果总是只有第一字符。本人就是由于这个原因，折腾了很久。在此记录一下，供大家以后参考！

例如：

CREATE PROCEDURE sp_AccountRole_Create
@CategoryID int,
@RoleName nvarchar(10),
@Description nvarchar(50),
@RoleID int output
AS
DECLARE @Count int
-- 查找是否有相同名称的记录
SELECT @Count = Count(RoleID) FROM Account_Role WHERE
RoleName = @RoleName
IF @Count = 0
INSERT INTO Account_Role
(CategoryID, RoleName, Description) valueS
(@CategoryID, @RoleName, @Description)
SET @RoleID = @@IDENTITY
RETURN 1
GO

SqlConnection DbConnection = new SqlConnection(mConnectionString);
SqlCommand command = new SqlCommand( "sp_AccountRole_Create", DbConnection );
DbConnection.Open(connectString);
// 废置SqlCommand的属性为存储过程
command.CommandType = CommandType.StoredProcedure;
command.Parameters.Add("@CategoryID", SqlDbType.Int, 4);
command.Parameters.Add("@RoleName", SqlDbType.NVarChar, 10);
command.Parameters.Add("@Description", SqlDbType.NVarChar, 50);
command.Parameters.Add("@RoleID", SqlDbType.Int, 4);
// 返回值
command.Parameters.Add("Returnvalue",
SqlDbType.Int,
4, // Size
ParameterDirection.Returnvalue,
false, // is nullable
0, // byte precision
0, // byte scale
string.Empty,
DataRowVersion.Default,
null );
command.parameters["@CategoryID"].value = permission.CategoryID;
command.parameters["@RoleName"].value = permission.PermissionName;
command.parameters["@Description"].value = permission.Description;
// 可以返回新的ID值
command.parameters["@RoleID"].Direction = ParameterDirection.Output;
int rowsAffected = command.ExecuteNonQuery();
int result = command.parameters["Returnvalue"].value;
int newID = command.parameters["@RoleID"].value;