C# 错误并非所有的代码路径都返回一个值，当执行查询时返回值就好了

2024-05-20 • 问答

我需要使用数据库中的信息填充数据网格，我有一个 dataaccess 类和正常的 form.cs 文件。当我执行查询本身时，它返回的值很好，但由于某种原因，它在运行时不会在代码槽 sp。我在 WindowsForms 中遇到了这个错误，我不太明白我做错了什么。我将首先展示我的 dataaccess 类

    public DataTable Sp_Teste()
    {

        try
        {
            ManageConnectionStateIbml1();
            SqlCommand command = new SqlCommand("SP_SELECT_DOCS_WHERE_JOBID_STATUS",connectionIBML1);
            command.CommandType = CommandType.StoredProcedure;
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            DataSet ds = new DataSet();
            adapter.Fill(ds);
            return ds.Tables[0];


        }
        catch (Exception ex)
        {
            Console.WriteLine("Erro: " + ex.Message);
        }
        finally
        {
            ManageConnectionStateIbml1();
            connectionIBML1.Close();
           
        }
       

    }

接下来是我的 Form.cs，因为我有 3 个数据网格视图，所以我将它们与区域分开。

        #region DatagridViewDocumentos
        dataGridViewDocumentos.DataSource = null;
        dataGridViewDocumentos.Columns.Clear();
        dataGridViewDocumentos.Refresh();
        DataTable dt = da.Sp_Teste();
        dataGridViewDocumentos.DataSource = dt;
        dataGridViewDocumentos.ColumnCount = 4;
        Datagridviewcolumn columnCaixa = dataGridViewDocumentos.Columns[0];
        columnCaixa.Width = 50;
        Datagridviewcolumn columnDOC = dataGridViewDocumentos.Columns[1];
        columnDOC.Width = 50;
        Datagridviewcolumn columnID = dataGridViewDocumentos.Columns[2];
        columnID.Width = 50;
        Datagridviewcolumn columnPROC = dataGridViewDocumentos.Columns[3];
        columnPROC.Width = 50;
        dataGridViewDocumentos.Columns[0].Name = "Caixa";
        dataGridViewDocumentos.Columns[1].Name = "DOC";
        dataGridViewDocumentos.Columns[2].Name = "ID";
        dataGridViewDocumentos.Columns[3].Name = "Proc";

       
        #endregion

希望有人能指出我的错误，谢谢。

在函数末尾添加 Return 语句。

finally
{
    ManageConnectionStateIbml1();
    connectionIBML1.Close(); 
}

return null;

public DataTable Sp_Teste()
{
    DataTable results = null;
    try
    {
        ManageConnectionStateIbml1();
        SqlCommand command = new SqlCommand("SP_SELECT_DOCS_WHERE_JOBID_STATUS",connectionIBML1);
        command.CommandType = CommandType.StoredProcedure;
        SqlDataAdapter adapter = new SqlDataAdapter(command);
        DataSet ds = new DataSet();
        adapter.Fill(ds);
        results = ds.Tables[0];


    }
    catch (Exception ex)
    {
       Console.WriteLine("Erro: " + ex.Message);
    }
    finally
    {
        ManageConnectionStateIbml1();
        connectionIBML1.Close();
       
    }
    return results;
}

我认为您只需要在将数据分配给 dataSource 属性后调用 gridview 的 DataBind() 方法即可。

#region DatagridViewDocumentos
    dataGridViewDocumentos.DataSource = null;
    dataGridViewDocumentos.DataBind();
    dataGridViewDocumentos.Columns.Clear();
    dataGridViewDocumentos.Refresh();
    DataTable dt = da.Sp_Teste();
    dataGridViewDocumentos.DataSource = dt;
    dataGridViewDocumentos.DataBind();
    dataGridViewDocumentos.ColumnCount = 4;
    DataGridViewColumn columnCaixa = dataGridViewDocumentos.Columns[0];
    columnCaixa.Width = 50;
    DataGridViewColumn columnDOC = dataGridViewDocumentos.Columns[1];
    columnDOC.Width = 50;
    DataGridViewColumn columnID = dataGridViewDocumentos.Columns[2];
    columnID.Width = 50;
    DataGridViewColumn columnPROC = dataGridViewDocumentos.Columns[3];
    columnPROC.Width = 50;
    dataGridViewDocumentos.Columns[0].Name = "Caixa";
    dataGridViewDocumentos.Columns[1].Name = "DOC";
    dataGridViewDocumentos.Columns[2].Name = "ID";
    dataGridViewDocumentos.Columns[3].Name = "Proc";

   
    #endregion

当您清除列然后绑定数据时，所以我认为这是造成问题，请考虑从网格中删除所有列后，如何访问它们，操作系统首先设置列然后绑定数据。

#region DatagridViewDocumentos
    dataGridViewDocumentos.DataSource = null;
    dataGridViewDocumentos.Columns.Clear();
    dataGridViewDocumentos.Refresh();

    DataGridViewColumn columnCaixa = new DataGridViewColumn("Caixa");
    columnCaixa.Width = 50;
    DataGridViewColumn columnDOC = new DataGridViewColumn("DOC");
    columnDOC.Width = 50;
    DataGridViewColumn columnID = new DataGridViewColumn("ID");
    columnID.Width = 50;
    DataGridViewColumn columnPROC = new DataGridViewColumn("Proc");
    columnPROC.Width = 50;

    dataGridViewDocumentos.columns.Add(columnCaixa);
    dataGridViewDocumentos.columns.Add(columnDOC );
    dataGridViewDocumentos.columns.Add(columnID );
    dataGridViewDocumentos.columns.Add(columnPROC );
    dataGridViewDocumentos.ColumnCount = 4;

    DataTable dt = da.Sp_Teste();
    dataGridViewDocumentos.DataSource = dt;
    #endregion

C# 错误并非所有的代码路径都返回一个值，当执行查询时返回值就好了

hanpangzi2234 回答：C# 错误并非所有的代码路径都返回一个值，当执行查询时返回值就好了

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