我正在使用Visual Studio 2017，Windows 10，并且正在ASP.NET上学习。
当我在空白的ASP.NET页（default.aspx）上添加一个webpartmanager和一个webpartzone时，出现错误（SQL错误）。我不知道此错误来自何处。
这是我的代码：
%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="WebApplication10.Default" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<style type="text/css">
.auto-style1 {
height: 160px;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<div>
</div>
<asp:WebPartManager ID="WebPartManager1" runat="server">
</asp:WebPartManager>
<table style="width: 100%; z-index: 1; left: 10px; top: 86px; position: absolute; height: 71px;">
<tr>
<td>
<asp:WebPartZone ID="WebPartZone1" runat="server" style="z-index: 1; left: 3px; top: 3px; position: absolute; height: 168px; width: 448px">
<ZoneTemplate>
<asp:Calendar ID="Calendar1" runat="server" style="z-index: 1; left: 3px; top: 26px; position: absolute; height: 223px; width: 442px" BackColor="White" BorderColor="#3366CC" BorderWidth="1px" CellPadding="1" DayNameFormat="Shortest" Font-Names="Verdana" Font-Size="8pt" ForeColor="#003399" Height="200px" Width="220px">
<DayHeaderStyle BackColor="#99CCCC" ForeColor="#336666" Height="1px" />
<NextPrevStyle Font-Size="8pt" ForeColor="#CCCCFF" />
<OtherMonthDayStyle ForeColor="#999999" />
<SelectedDayStyle BackColor="#009999" Font-Bold="True" ForeColor="#CCFF99" />
<SelectorStyle BackColor="#99CCCC" ForeColor="#336666" />
<TitleStyle BackColor="#003399" BorderColor="#3366CC" BorderWidth="1px" Font-Bold="True" Font-Size="10pt" ForeColor="#CCCCFF" Height="25px" />
<TodayDayStyle BackColor="#99CCCC" ForeColor="White" />
<WeekendDayStyle BackColor="#CCCCFF" />
</asp:Calendar>
</ZoneTemplate>
</asp:WebPartZone>
</td>
<td> </td>
<td> </td>
</tr>
<tr>
<td class="auto-style1"></td>
<td class="auto-style1"></td>
<td class="auto-style1"></td>
</tr>
<tr>
<td> </td>
<td> </td>
<td> </td>
</tr>
</table>
</form>
</body>
</html>
provider: SQL Network Interfaces, error: 26
[SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)]
System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling, SqlAuthenticationProviderManager sqlAuthProviderManager) +907
System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions) +5967828
System.Data.ProviderBase.DbConnectionFactory.CreateNonPooledConnection(DbConnection owningConnection, DbConnectionPoolGroup poolGroup, DbConnectionOptions userOptions) +38
System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) +507
System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +154
System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +21
System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry) +90
System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry) +443
System.Data.SqlClient.SqlConnection.Open() +96
System.Web.Management.SqlServices.GetSqlConnection(String server, String user, String password, Boolean trusted, String connectionString) +75
[HttpException (0x80004005): Unable to connect to SQL Server database.]
System.Web.Management.SqlServices.GetSqlConnection(String server, String user, String password, Boolean trusted, String connectionString) +125
System.Web.Management.SqlServices.SetupApplicationServices(String server, String user, String password, Boolean trusted, String connectionString, String database, String dbFileName, SqlFeatures features, Boolean install) +89
System.Web.Management.SqlServices.Install(String database, String dbFileName, String connectionString) +29
System.Web.DataAccess.SqlConnectionHelper.CreateMdfFile(String fullFileName, String dataDir, String connectionString) +386
在此示例中，当我尝试相同的youtube视频时。我遇到了同样的错误。