C＃注册

Question

我的项目C＃遇到问题，我想注册用户，但不起作用！ 有人知道我该如何解决这个问题，谢谢。

errorSystem.Data.SqlClient.SqlException（0x80131904）：无法将值NULL插入表'D：\\ ASP_WORKSPACES \\ LOGIN \\ LOGIN \\ APP_DATA \\ DATABASE.MDF.dbo.User'的列'Id'中； 列不允许为空。 INSERT失败。 该语句已终止。 àSystem.Data.SqlClient.SqlConnection.OnError（SqlException异常，布尔值breakConnection，操作1 wrapCloseInAction) à System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action 1 wrapCloseInAction）àSystem.Data.SqlClient.TdsParser .ThrowExceptionAndWarning（TdsParserStateObject stateObj，Boolean callerHasConnectionLock，Boolean asyncClose）àSystem.Data.SqlClient.TdsParser.TryRun（RunBehavior runBehavior，SqlCommand cmdHandler，SqlDataReader dataStream，BulkCopySimpleResultSet bulkCopyHandler，TdsParserStateObjectState.à FinishExecuteReader（SqlDataReader ds，RunBehavior runBehavior，字符串resetOptionsString，布尔值isInternal，布尔型forDescribeParameterEncryption） Re 尝试，SqlDataReader ds，布尔describeParameterEncryptionRequest）àSystem.Data.SqlClient.SqlCommand.RunExecuteReader（CommandBehavior cmdBehavior，RunBehavior runBehavior，布尔returnStream，字符串方法，TaskCompletionSource 1 completion, Int32 timeout, Task& task, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry) à System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource 1完成，字符串methodName，布尔sendToPipe，Int32超时，布尔＆usedCache，布尔asyncWrite，布尔inRetry）àSystem.Data.SqlClient.SqlCommand.ExecuteNonQuery（）àRegistration.Button1_Click（对象发送方，EventArgs e）dans D：\\ asp_workspaces \\ login \\ login \\ Registration.aspx.cs：ligne 49 ClientConnectionId：b0d4edc1-2ade-4417-8d9d-7f6e8befc17e错误编号：515，状态：2，类：16

Register.aspx.cs的代码

    protected void Button1_Click(object sender, EventArgs e)
{

    try
    {
        SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["RegistrationConnectionString"].ConnectionString);
        conn.Open();
        string insertQuery = ("insert into [User](username,email,password,country)values (@username,@email,@password,@country)");
        SqlCommand cmd = new SqlCommand(insertQuery, conn);

        cmd.Parameters.AddWithValue("@username", username.Text);
        cmd.Parameters.AddWithValue("@email", email.Text);
        cmd.Parameters.AddWithValue("@password", password.Text);
        cmd.Parameters.AddWithValue("@country", country.SelectedItem.ToString());
        cmd.ExecuteNonQuery();

        Response.Write("User Successfully Registered");

        conn.Close();
    }
    catch (Exception ex)
    {
        Response.Write("error" + ex.ToString());
    }

}

Registration.aspx

<form id="form1" runat="server">
    <div>
        <table class="auto-style1">
            <tr>
                <td class="auto-style3">User name</td>
                <td class="auto-style4">
                    <asp:TextBox ID="username" runat="server" Height="22px" Width="180px"></asp:TextBox>
                </td>
                <td>
                    <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="username" ErrorMessage="Username is required." ForeColor="#FF3300"></asp:RequiredFieldValidator>
                </td>
            </tr>
            <tr>
                <td class="auto-style3">E-mail</td>
                <td class="auto-style4">
                    <asp:TextBox ID="email" runat="server" Width="180px"></asp:TextBox>
                </td>
                <td>
                    <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="email" ErrorMessage="Email is required." ForeColor="#FF3300"></asp:RequiredFieldValidator>
                    <br />
                    <asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ControlToValidate="email" ErrorMessage="You must enter the valid email." ForeColor="#FF3300" ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"></asp:RegularExpressionValidator>
                </td>
            </tr>
            <tr>
                <td class="auto-style3">Password</td>
                <td class="auto-style4">
                    <asp:TextBox ID="password" runat="server" TextMode="Password" Width="180px"></asp:TextBox>
                </td>
                <td>
                    <asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ControlToValidate="password" ErrorMessage="Password is required." ForeColor="#FF3300"></asp:RequiredFieldValidator>
                </td>
            </tr>
            <tr>
                <td class="auto-style3">Confirm Password</td>
                <td class="auto-style4">
                    <asp:TextBox ID="confpassword" runat="server" TextMode="Password" Width="180px"></asp:TextBox>
                </td>
                <td>
                    <asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server" ControlToValidate="confpassword" ErrorMessage="Confirm Password is required." ForeColor="#FF3300"></asp:RequiredFieldValidator>
                    <br />
                    <asp:CompareValidator ID="CompareValidator1" runat="server" ControlToCompare="password" ControlToValidate="confpassword" ErrorMessage="Password must be some" ForeColor="#FF3300"></asp:CompareValidator>
                </td>
            </tr>
            <tr>
                <td class="auto-style3">Country</td>
                <td class="auto-style4">
                    <asp:DropDownList ID="country" runat="server" Width="180px">
                        <asp:ListItem>Select country</asp:ListItem>
                        <asp:ListItem>USA</asp:ListItem>
                        <asp:ListItem>UK</asp:ListItem>
                        <asp:ListItem>Germany</asp:ListItem>
                        <asp:ListItem>France</asp:ListItem>
                    </asp:DropDownList>
                </td>
                <td>
                    <asp:RequiredFieldValidator ID="RequiredFieldValidator5" runat="server" ControlToValidate="country" ErrorMessage="Select the country name." ForeColor="#FF3300" InitialValue="Select country"></asp:RequiredFieldValidator>
                </td>
            </tr>
            <tr>
                <td class="auto-style2">&nbsp;</td>
                <td class="auto-style5">
                    <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Submit" />
                    <input id="Reset1" type="reset" value="reset" /></td>
                <td>&nbsp;</td>
            </tr>
            <tr>
                <td class="auto-style2">&nbsp;</td>
                <td class="auto-style5">&nbsp;</td>
                <td>&nbsp;</td>
            </tr>
        </table>
    </div>
</form>

在Visual Studio 2017中查询创建数据库SQL

CREATE TABLE [dbo].[User] (
[Id]       INT        NOT NULL DEFAULT 1,
[username] NCHAR (20) NULL DEFAULT u,
[email]    NCHAR (20) NULL DEFAULT e,
[password] NCHAR (20) NULL DEFAULT p,
[country]  NCHAR (20) NULL DEFAULT c,
PRIMARY KEY CLUSTERED ([Id] ASC)
);

Answer 1

错误非常明显，您不能在列Id插入null 。 最简单的解决方案是更改表定义，以使该列为IDENTITY列，当您插入新行时，该列会自动递增值。 因此，将您的定义更改为：

CREATE TABLE [dbo].[User] (
    [Id]       INT        NOT NULL IDENTITY(1, 1), 
    [username] NCHAR (20) NULL,
    [email]    NCHAR (20) NULL,
    [password] NCHAR (20) NULL,
    [country]  NCHAR (20) NULL,
    PRIMARY KEY CLUSTERED ([Id] ASC)
);

Answer 2

您有一个表Users，其ID列不能为空值（如Error所解释）。

您要么需要通过插入查询为ID列发送一些值，例如

Insert into [User] ([Id], [username], …) values (@id, @username……)

并以与添加其他用户值相同的方式添加参数。 或使数据库列ID为ID，增量Seed value =1 。

假设Id是您的主键列，则分配default =1并不是一个很好的选择。