DataGridView导入Excel时，出现了“未将对象引用设置到对象的实例”的解决办法

print?for (int i = 0; i < iRows - 1; i++)
{
     for (int j = 1, k = 0; j < iCols; j++)
     {
         if (dgvStudent.Columns[j].Visible)
         {

                 dimArray[i + 1, k] = dgvStudent.Rows[i].Cells[j].Value.ToString();
                 k++;

         }
     }
}

               for (int i = 0; i < iRows - 1; i++)
                {
                    for (int j = 1, k = 0; j < iCols; j++)
                    {
                        if (dgvStudent.Columns[j].Visible)
                        {

                                dimArray[i + 1, k] = dgvStudent.Rows[i].Cells[j].Value.ToString();
                                k++;

                        }
                    }
                }[csharp] view plaincopyprint?//其中public System.Windows.Forms.DataGridView dgvStudent;，dimArray为Excel中的单元格，即

//其中public System.Windows.Forms.DataGridView dgvStudent;，dimArray为Excel中的单元格，即[csharp] view plaincopyprint?//ws.get_Range(ws.Cells[1, 1], ws.Cells[iRows, iCols]).Value2 = dimArray;

//ws.get_Range(ws.Cells[1, 1], ws.Cells[iRows, iCols]).Value2 = dimArray;[csharp] view plaincopyprint?//ws 为Microsoft.Office.Interop.Excel.Worksheet

//ws 为Microsoft.Office.Interop.Excel.Worksheet
这是从Datagridview导入Excel时的代码，但是出现了“未将对象引用设置到对象的实例”这个错误，我以为是不是我手动添加列时添加的不正确，所以我把函数 dgvStudent.Columns.Add(列名字符串变量, 列头名称字符串变量);改为了

[csharp]
DataGridViewTextBoxColumn column = new DataGridViewTextBoxColumn();
               column.HeaderText = sh;
               column.Name = quesId;
               column.ReadOnly = false;
               dgvStudent.Columns.Add(column);

DataGridViewTextBoxColumn column = new DataGridViewTextBoxColumn();
                column.HeaderText = sh;
                column.Name = quesId;
                column.ReadOnly = false;
                dgvStudent.Columns.Add(column);不用DataGridViewColumn column = new DataGridViewColumn();由于会出现CellType为空的错误。

但是还会有“未将对象引用设置到对象的实例”错误，因此不是手动添加列的错误。此时定位到Datagridview单元格与Excell的关系，

[csharp]
for (int i = 0; i < iRows - 1; i++)
               {
                   for (int j = 1, k = 0; j < iCols; j++)
                   {
                       if (dgvStudent.Columns[j].Visible)
                       {
                           if (dgvStudent.Rows[i].Cells[j].ValueType == typeof(string))
                           {
                               dimArray[i + 1, k] = dgvStudent.Rows[i].Cells[j].Value.ToString();
                               k++;
                           }
                           else//很重要，因为DataGridView单元格有null的时候
                           {
                               if (dgvStudent[j, i].Value == null)
                               {
                                   dgvStudent[j, i].Value = string.Empty;

补充：软件开发 , C# ,