Question

下面的代码是web方法（最常见的是你可以在任何地方看到它），但我不断从标题中得到错误。我刚开始使用.NET，所以如果有人能指出我正确的方向，请这样做。

SqlConnection myConnection = new SqlConnection(ConfigurationManager.ConnectionStrings["mySQLconn"].ConnectionString);

[WebMethod(Description = "Select Customers")]
    public string GetVersionofSelectedCustomer(string versionEmail)
    {

        string select = "SELECT version FROM customer WHERE EMAIL = '" + versionEmail + "'";
        SqlDataAdapter adapter = new SqlDataAdapter(select, myConnection);

        DataSet custDS = new DataSet();            
        //adapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;
        adapter.Fill(custDS, "Customers");

        return custDS;

    }

连接在Web.config（本地连接）中定义，返回custDS; 是失败的地方。

Answer 1

您正在返回数据集，因此您应该将返回类型用作Dataset

public Dataset GetVersionofSelectedCustomer(string versionEmail)
{
    //add your code to return dataset
}

Answer 2

您的函数的返回类型为string，并且您尝试返回DataSet对象。你可以尝试这样：

public DataSet GetVersionofSelectedCustomer(string versionEmail)
{
     string select = "SELECT version FROM customer WHERE EMAIL = '" + versionEmail + "'";
     SqlDataAdapter adapter = new SqlDataAdapter(select, myConnection);

     DataSet custDS = new DataSet();            
     //adapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;
     adapter.Fill(custDS, "Customers");

     return custDS;

}

Answer 3

您的方法签名返回一个字符串，但是您正在返回一个DataSet - 它不清楚您想在这里做什么 - 可能只是更改签名以返回数据集？

无法将类型'System.Data.DataSet'隐式转换为'string'

3 个答案: