asp.net c#里如何使用 varchar(max) 参数

最新推荐文章于 2024-12-06 11:27:48 发布

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最新推荐文章于 2024-12-06 11:27:48 发布

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原文链接：http://www.cnblogs.com/adandelion/archive/2009/07/27/1532242.html

本文介绍在ASP.NET和C#中如何处理大型字符串数据，特别是如何使用SqlParameter来操作SQL Server中的nvarchar(max)类型。通过示例展示了如何设置存储过程参数及执行存储过程来获取长文本数据。

asp.net c#里如何使用 varchar(max) 参数

SqlParameter paramSummary =
new SqlParameter("@DocumentSummary",
SqlDbType.VarChar, -1);

MSDN完整的例子：

CREATE PROCEDURE GetDocumentSummary
(
    @DocumentID int,
    @DocumentSummary nvarchar(MAX) OUTPUT
)
AS
SET NOCOUNT ON
SELECT  @DocumentSummary=Convert(nvarchar(MAX), DocumentSummary)
FROM    Production.Document
WHERE   DocumentID=@DocumentID

Code
static private string GetDocumentSummary(int documentID)
{
    //Assumes GetConnectionString returns a valid connection string.
    using (SqlConnection connection =
               new SqlConnection(GetConnectionString()))
    {
        connection.Open();
        SqlCommand command = connection.CreateCommand();
        try
        {
            // Setup the command to execute the stored procedure.
            command.CommandText = "GetDocumentSummary";
            command.CommandType = CommandType.StoredProcedure;

            // Set up the input parameter for the DocumentID.
            SqlParameter paramID =
                new SqlParameter("@DocumentID", SqlDbType.Int);
            paramID.Value = documentID;
            command.Parameters.Add(paramID);

            // Set up the output parameter to retrieve the summary.
            SqlParameter paramSummary =
                new SqlParameter("@DocumentSummary",
                SqlDbType.NVarChar, -1);
            paramSummary.Direction = ParameterDirection.Output;
            command.Parameters.Add(paramSummary);

            // Execute the stored procedure.
            command.ExecuteNonQuery();
            Console.WriteLine((String)(paramSummary.Value));
            return (String)(paramSummary.Value);
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
            return null;
        }
    }
}

这里有更详尽的例子：Working with Large Value Types
http://msdn.microsoft.com/en-us/library/a1904w6t(VS.80).aspx

转载于:https://www.cnblogs.com/adandelion/archive/2009/07/27/1532242.html